Compared to a hydrocarbon chain where all the carbon atoms are linked by single bonds, a hydrocarbon chain with the same number of carbon atoms, but with one or more double bonds, will .

Be more constrained in structure

Explanation:

This is because double bonds confer unsaturation on an organic molecules. The molecules are more ordered as they have lesser number of hydrogen atoms in them.

Having same number of carbon atoms means they are corresponding molecules.

For example. Ethyne is corresponding to ethane. Since ethyne has less number of hydrogen atoms than ethane, it will be more constrained in structure than ethane.

the answer is d.) potassium