check the box under each molecule in the table below that is an isomer of this molecule: if there are no…

Explanation:

Step1: Recall isomer definition

Isomers have same molecular formula but different structures. First, find the molecular formula of the given molecule. Assume it's a hydrocarbon with carbon - carbon double bonds. Count the number of carbon and hydrogen atoms. Let's say the given molecule has 6 carbon atoms and 10 hydrogen atoms ($C_6H_{10}$).

Step2: Analyze first molecule in table

The first molecule in the table is a cyclo - hexane ($C_6H_{12}$). Since its molecular formula is different from $C_6H_{10}$, it is not an isomer.

Step3: Analyze second molecule in table

The second molecule is a methyl - cyclopentene. Its molecular formula is also different from $C_6H_{10}$, so it is not an isomer.

Step4: Analyze third molecule in table

The third molecule is a linear di - ene. Counting the carbon and hydrogen atoms, it has 6 carbon atoms and 10 hydrogen atoms ($C_6H_{10}$). It has a different structure from the given molecule, so it is an isomer.

Step5: Analyze fourth molecule in table

The fourth molecule is also a linear di - ene with 6 carbon atoms and 10 hydrogen atoms ($C_6H_{10}$). It has a different structure from the given molecule, so it is an isomer.

Answer:

Check the box under the third and fourth molecules in the table.