What is true about the about the structure or function of the plasma membrane a. large molecules often cross the plasma membrane while inside vesicles b. hydrophobic molecules keep the cell from getting too much water c. the bilayer structure forms a solid boundery that seperates the cell from its enviornment. d. its made entirely of intregral protiens.

The answer is C. The bilayer structure forms  a solid boundary that separates the cell from its environment.

Large molecules do not cross the membrane through vesicles but through carrier proteins. Option B. is entirely false as hydrophobic molecules never get in contact with water, they are 'water hating' unlike hydrophilic molecules.
The plasma membrane is made of both integral and peripheral proteins.

Hope it helped!