Answer
a) Isomers
b) Same molecule
c) Same molecule
Work Step by Step
a) These two molecules have same molecular formula but the structure is different and also the IUPAC name is different. One having name: methyl propanoate and other : Ethyl ethanoate. Clearly, these are isomers.
b) Same Molecular formula and structure. IUPAC nomenclature is same. 2-pentyne. They are same molecule.
c) These two molecules are same as their structure and molecular formula both are same. IUPAC nomenclature : Ethanoic acid.
