Which Explanation Best Describes the Asymmetrically Oriented Structure of the Proteins

Which explanation best describes the asymmetrically oriented structure of the proteins in the cell membrane?

A) Each type of protein has its own function.
B) These proteins are manufactured by free ribosomes.
C) These proteins are initially formed by ribosomes on the rough ER.
D) These proteins pass through the ER membrane into the ER lumen.
E) Enzymes are needed to modify the carbohydrate chains on these proteins.