What is another name for the phospholipid bilayer?
a.) permeable membrane
b.) protein membrane
c.) plasma membrane
d.) lipid membrane

The answer is D.

The reason for this is, as stated in your question, it is called a phospholipid bilayer.

It's called like that because it is made out of lipids and it also has phosphate groups, while the bilayer part means it just has two layers.Therefore it is commonly also called a lipid membrane. 

Cuz i said so. which gives it to b