So based on the given figure above, here are the compounds represented by each of the following structural formulas:
A. Pentane - It is classified as pentane because it is a straight chain having 5 carbons.
B. 3-methylpentane -It is a straight chain with five carbons plus a methyl group (CH3).
C. 2,5-dimethylhexane - the longest chain consists of 6 carbons (hexane) and on carbon 2 and 5, each have a methyl as a side chain.
Hope these answers help.