Question

What prohibits lipids from being a readily available energy source? Fat must be broken down into fatty acids before being converted to glucose. Lipids are structural components, so they are a last-resort energy source. Lipids are only used to create enzymes, hormones, and antibodies. The conversion of fat to glucose is controlled by insulin.

Answer 1

Lipids are really hard to break down because they have strong bonds between the carbon atoms. Despite that through a series of metabolic processes they can be converted into fatty acids and then into glucose (and then converted into glycogen). 

From your list, it would be:
a. Fat must be broken down into fatty acids before being converted to glucose