Pentane (C5H12) 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.