How many structure isomers can you draw for pentane?

A. 2

B. 3

C. 4

D. 5

Answer

Pentane (C5​H12​) is an organic compound and an alkane with five carbon atoms. Pentane has three structural isomers. These are n-pentane, Iso-pentane and neo-pentane.
Pentane means exclusively the n-pentane isomer; the other two being called isopentane (methylbutane) and neopentane (dimethylpropane). Cyclopentane is not an isomer of pentane. 
Structures of all the three isomers are given here.
Option B is correct.