what are the branch-chain Alkanes?

Answer:
The top branch-chain is a Isobutane branch. And the bottom branch chain is a  Neopentane branch
A branched chained alkane or branched alkane is an alkane which has alkyl groups bonded to its central carbon chain. Branch alkanes contain only carbon and hydrogen (c and h) atoms, with cartons connected other carbons by single bonds only, but the molecules contain branches (methyl, ethyl, etc.) so they are not linear.