Which factor causes the shapes of saturated and unsaturated fatty acids to differ?

The correct answer will be- double bond in fatty acids.

Explanation:

Two types of fatty acids are present in nature: saturated and unsaturated fatty acids.

The saturated fatty acid is a molecule which gets saturated with the maximum number of hydrogen atoms the carbon skeleton can have whereas unsaturated fatty acid exhibit a double bond in their structure which cause the bending of the carbon skeleton due to different bending angle.

The double bond provides different shape to the unsaturated fatty acid which is absent in the saturated fatty acids.

Thus, the double bond in a fatty acid is the correct answer.

i think the answer would be d