What is the key difference between saturated and unsaturated fats?

A. Saturated fats are usually liquid at room temperature; unsaturated fats are usually solid

B. Saturated fats stay solid at room temperature; unsaturated fats are usually liquid

C. Saturated fats can be found in vegetable oils, unsaturated fats can be found in animal products

D. Saturated fats are healthier than unsaturated fats