A. Chlorine molecule
B. Ammonia molecule
C. Methane molecule
D. Water molecule
A chlorine molecule contains the fewest covalent bonds among the options provided. It consists of two chlorine atoms bonded together by a single covalent bond. Compared with the other options, ammonia has three covalent bonds, methane has 4 while water has 2.
Therefore, the Correct Answer is A.