Answer:
The answer to your question is letter A.
Step-by-step explanation:
Isomers are molecules that have the same molecular formula but have a different structure. The molecule from which are looking an isomer has 5 carbons and 1 double bond. Then we need to look for another molecule with these components.
A.- This molecule has 5 carbons and 1 double bond, This structure is an isomer of the first one.
B.- This molecule has 3 carbons and 1 double bond, it's not an isomer of the first structure.
C. This molecule has 4 carbons and 1 triple bonds, it's not an isomer of the first structure.
D. This molecule has 5 carbons but it doesn't have any double bond, then it's not an isomer of the first structure.