Draw the structure of a compound with molecular formula c5h12 that exhibits only one kind of proton (all 12 protons are chemically equivalent).

The middle carbon is 4-degree since it is attached to 4 carbons. All other carbons are 1-degree since they are attached to only 1 carbon. 

Hydrogens attached with 1-degree carbon are all same. Hydrogen are often refereed to as protons. No carbon is attached to 4-degree carbon. So all hydrogens in this structure are same.

This structure is called  NeoPentane

Which of the following did you identify correctly