The isomeric pair is (a) ethane and propane (b) propane and butane (c) ethane and ethane (d) butane and 2-methyl propane
butane and 2-methyl propane. Butane and 2-methyl propane is an isomeric pair as both consist of 4 atoms of carbon and 10 atoms of hydrogen. They have the same molecular formula, i.e. C4H10. Hence, the correct option is (d).
