Answer: b. micelles
Step-by-step explanation:
Phospholipids are lipids that contain a polar part, which is hydrophilic (i.e. likes water) and a non-polar part, which is hydrophobic (i.e. dislikes water).
When phospholipids are in an aqueous environment they form a structure called micelle, in which the polar heads face the water molecules and surround the non-polar tails which remain on the inside. This way, the polar heads protect the hydrophobic chains from exposure to the aqueous environment.
I've attached an image of a micelle for better understanding of its structure.