Which of the following refers to a condition in which a patient experiences difficulty breathing while lying down, but their breathing improves when they sit up or stand?

A. Helper T cells.

B. B cells.

C. Natural killer cells.

D. Cytotoxic T cells .

Natural killer cells.

Natural killer (NK) cells are large granular lymphocytes that are capable of destroying cells infected by viruses or bacteria and susceptible tumor cells without prior sensitization and restriction by MHC antigens.

Helper T cells (choice A) are a type of white blood cell that helps other immune cells respond to infections but do not directly kill infected or tumor cells.

B cells (choice B) are a type of white blood cell that produces antibodies to fight infections but do not directly kill infected or tumor cells.

Cytotoxic T cells (choice D) are a type of white blood cell that can kill infected or tumor cells but require prior sensitization to do so.

A. A short piece of double-stranded DNA that binds to the template DNA and acts as a "starter" for the polymerase.

B. A short piece of double-stranded DNA that binds to the primer and acts as a "starter" for the template.

C. A short piece of single-stranded DNA that binds to the template DNA and acts as a "starter" for the polymerase.

D. A short piece of single-stranded DNA that binds to the polymerase and acts as a "starter" for the template.

A primer is a short single-stranded DNA fragment used in certain laboratory techniques, such as the polymerase chain reaction (PCR).

In the PCR method, a pair of primers hybridizes with the sample DNA and defines the region that will be amplified.

Choice A) A short piece of double-stranded DNA that binds to the template DNA and acts as a “starter” for the polymerase is incorrect because primers are single-stranded, not double-stranded.

Choice B) A short piece of double-stranded DNA that binds to the primer and acts as a “starter” for the template is incorrect because it does not make sense for a primer to bind to itself.

Choice D) A short piece of single-stranded DNA that binds to the polymerase and acts as a “starter” for the template is incorrect because primers bind to the template DNA, not to the polymerase.

Note: DNA primers are used instead of RNA primers in DNA sequencing and PCR because DNA is more stable, specific, and compatible with the enzymes and processes involved in these techniques.

A. Use a large sample size and a standardized procedure for administering the medications.

B. Use a placebo group and a double-blind technique for giving the medications.

C. Use a matched-pairs design and a crossover technique for switching the medications.

D. Use a convenience sample and a pretest-posttest design for measuring the pain levels.

The correct answer is choice B.

Using a placebo group and a double-blind technique for giving the medications is the best way to ensure that the study is valid and reliable.

A placebo group helps control for the placebo effect, which can influence the results of a study.

A double-blind technique means that neither the patients nor the researchers know which medication is being given, reducing bias.

Choice A is not the best answer because while a large sample size and standardized procedure can increase reliability, they do not address validity.

Choice C is not the best answer because a matched-pairs design and crossover technique are useful for reducing variability but do not address validity.

Choice D is not the best answer because a convenience sample may not be representative and a pretest-posttest design does not control for extraneous variables.

A. They are the same.

B. Atomic mass is always greater than mass number.

C. Atomic mass and mass number are not related.

D. Atomic mass is very close to mass number but with some deviation in the decimal places.

Atomic mass is very close to mass number but with some deviation in the decimal places.

Atomic mass is also known as atomic weight and is the weighted average mass of an atom of an element based on the relative natural abundance of that element’s isotopes.

The mass number, on the other hand, is a count of the total number of protons and neutrons in an atom’s nucleus.

Choice A is incorrect because atomic mass and mass number do not mean the same thing.

Choice B is incorrect because atomic mass is not always greater than mass number.

Choice C is incorrect because atomic mass and mass number are related.

A. Ribosome

B. Nucleus

C. Mitochondria

D. Plasma membrane.

The plasma membrane is the organelle that encapsulates the contents of the cell and plays a vital role in regulating the movement of substances in and out of the cell.

It is a selectively permeable barrier that separates the internal environment of the cell from the external environment.

Choice A is incorrect because ribosomes are organelles involved in protein synthesis, not in regulating the movement of substances in and out of the cell.

Choice B is incorrect because the nucleus is an organelle that contains the cell’s genetic material, not in regulating the movement of substances in and out of the cell.

Choice C is incorrect because mitochondria are organelles involved in energy production, not in regulating the movement of substances in and out of the cell.

A. Rapid recruitment of immune cells to sites of infection and inflammation

B. Antigen-independent defense mechanism

C. Immunologic memory

D. Non-specific host-defense mechanisms .

Immunologic memory is the hallmark of adaptive immunity.

Immunologic memory enables the host to mount a more rapid and efficient immune response upon subsequent exposure to the antigen.

Choice A is incorrect because rapid recruitment of immune cells to sites of infection and inflammation is a characteristic of innate immunity.

Choice B is incorrect because antigen-independent defense mechanisms are characteristic of innate immunity.

Choice D is incorrect because non-specific host-defense mechanisms are characteristic of innate immunity.

A. Particles have a decrease in mobility.

B. The fluid will have a lower density.

C. The fluid will have a higher flow rate.

D. The fluid will have a higher pressure.

The correct answer is choice A.

An increase in viscosity of a fluid results in a decrease in mobility of particles.

Viscosity is the resistance of a fluid to a change in shape or movement of neighboring portions relative to one another.

It denotes opposition to flow and may be thought of as internal friction between the molecules.

Choice B is incorrect because an increase in viscosity does not affect the density of a fluid.

Choice C is incorrect because an increase in viscosity results in a decrease, not an increase, in flow rate.

Choice D is incorrect because an increase in viscosity does not affect the pressure of a fluid.

A. Proton

B. Neutron

C. Electron

D. Nucleon

Protons contribute to the positive charge of an atom.

Protons are subatomic particles with a positive charge found in the nucleus of an atom.

Choice B is incorrect because neutrons are neutral and do not have a charge. Choice C is incorrect because electrons have a negative charge.

Choice D is incorrect because nucleons refer to both protons and neutrons, but only protons contribute to the positive charge of an atom.

A. Because water dissolves all solutes equally well.

B. Because water is a nonpolar solvent.

C. Because water is good at dissolving ions and polar molecules.

D. Because water is poor at dissolving nonpolar molecules.

Water is sometimes called the “universal solvent” because it dissolves more substances than any other liquid.

This is due to its polarity and ability to form hydrogen bonds, which allows it to dissolve ions and polar molecules.

Choice A) Because water dissolves all solutes equally well is incorrect because water does not dissolve all solutes equally well.

Choice B) Because water is a nonpolar solvent is incorrect because water is a polar solvent.

Choice D) Because water is poor at dissolving nonpolar molecules is incorrect because it does not explain why water is called the “universal solvent”.

A. Oogenesis.

B. Fertilization.

C. Meiosis.

D. Mitosis.

Fertilization.

Fertilization is the process by which male and female gametes fuse to form a zygote.

Oogenesis (choice A) is the process by which female gametes, or eggs, are produced.

Meiosis (choice C) is a type of cell division that results in the formation of gametes.

Mitosis (choice D) is a type of cell division that results in the formation of two identical daughter cells.