Roles cholesterol plays in the plasma membrane

What are roles cholesterol plays in the plasma membrane?
(multiple responses are correct)
Select one or more:
a. Cholesterol serves as the framework in which the other components of the membrane are embedded.
b. Cholesterol prevents their interaction and possible crystallization of the plasma membrane especially in cold temperatures.
c. Cholesterol’s rigid, planar portion of the molecule tends to block many of the motions of the first portions of the fatty acid chains in the phospholipid bilayer.
d. Cholesterol makes the intermediate portion of the bilayer more rigid and less permeable to small, polar molecules