If the plasma membrane were only made of phospholipids witho

If the plasma membrane were only made of phospholipids, without any membrane proteins, then.... only molecules that can move by facilitated diffusion would get across. only molecules that are moving against a concentration gradient would get across. only molecules that can move by simple diffusion would get across. all movement of molecules would stop. only molecules that are moving with a concentration gradient would get across.

Solution

The answer is: Only molecules that are moving with a concentration gradient would get across.

If the plasma membrane were only made of phospholipids, without any membrane protein , then only molecules that are moving with a concentration gradient will get across. This is because, passive transport does not require involvement of membrane proteins, while active transport and facilitated diffusion do require.