Lipids, mainly phospholipids, make up the bulk of the cell membrane. how is the structure of the phospholipid so perfectly paired to the function of the cell membrane?
a) phospholipids are bulky/large molecules that prevent all molecules from entering/exiting the cell.
b) the polar tails of the phospholipids provide the barrier between the exterior/interior hydrophilic environments.
c) lipids contain high energy bonds, and these bonds to provide the energy to move molecules across the membrane.
d) the head of the phospholipid, which is hydrophilic, to control the movement of large hydrophobic molecules, and the tails of the phospholipid, which are hydrophobic, to control the movement of large hydrophilic molecules.

The lipid bilayer in the cell membrane helps is the multiple functions executed by the membrane. The bilayer organization of the phospholipids in the membrane controls the movements of the different molecules in and out of the cell. The phospholipid have a hydrophobic end and a hydrophilic end. The hydrophilic ends of these phospholipids are in contact with the inside and the outside of the cell, while the hydrophobic parts are towards the center of the bilayer. The hydrophilic end controls the movement of the large hydrophobic molecules, and the hydrophobic tails controls the movement of large hydrophilic molecules.

Hence, the answer is 'Option D'.

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."