d. Butane
Explanation:
The question is asking about the chain isomerism of the compounds.
a. Methane - have 1 carbon atom and does not have isomers.
c. Propane - have 3 carbon atoms and does not have isomers.
b. Ethane - have 2 carbon atoms and does not have isomers.
d. Butane - have 5 carbon atoms and does have two isomers.
You may find the structure of the isomers in the attached picture.
Learn more about:
structure of organic compounds
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