In a plasma membrane, how do the tails of the phospholipid molecules line up?

they alternate with the heads.
they stick out with the heads in the center.
they tangle randomly to form a fiber.
they are sandwiched between two layers of heads.

They are sandwiched between two layers of heads. Recall that the heads are hydrophilic therefore they will always be on the outside and the tails are hydrophobi therefore they willl always be away from water, there fore sandwiched. I'm a bio major, hope I helped :)