which shows an isomer of the molecule below?

Answer:

B.

Explanation:

Step1: Define isomers

Isomers have same molecular formula but different structures. The given molecule is a 4 - carbon alkene.

Step2: Analyze option A

Option A is an alkane (no double bond), so it has a different molecular formula (more hydrogens) and is not an isomer.

Step3: Analyze option B

Option B has the same number of carbon and hydrogen atoms as the given alkene and a different structure, making it an isomer.

Step4: Analyze option C

Option C has 3 carbons, so it has a different molecular formula and is not an isomer.

Step5: Analyze option D

Option D is an alkyne (triple bond), so it has a different molecular formula (fewer hydrogens) and is not an isomer.