What is the difference between isopentane and neopentane structures?

Both isopentane and neopentane have the same chemical formula ${\mathrm{C}}_5{\mathrm{H}}_{12}$.  

Isopentane is a five-carbon-atom chemical with a single branching chain. The structure of isopentane is 

Neopentane is a chemical compound having five carbon atoms and two or more branching chains. The structure of neopentane is -

The structure of isopentane differs from that of neopentane in that isopentane has a four-membered carbon chain with a single methyl group attached to the second carbon atom. Neopentane, on the other hand, has four methyl groups connected to a carbon atom in the middle. Thus, the correct option is D.