Answer:
D) 5
Explanation:
In this case, the "monobromination" is the addition of one "Br" to the molecule. With this in mind, we have to explore each option to put this "Br" atom:
1) (bromomethyl)cyclopentane = The Br atom is placed in carbon 6
2) 1-bromo-1-methylcyclopentane = The Br atom is placed in carbon 1
3) (1R,2R)-1-bromo-2-methylcyclopentane = The Br atom is placed in carbon 2 (with trans configuration)
4) (1R,2S)-1-bromo-2-methylcyclopentane = The Br atom is placed in carbon 2 (with cis configuration)
5) 1-bromo-3-methylcyclopentane = The Br atom is placed in carbon 3
See figure 1
I hope it helps!