Choose the correct answer from the list below. Not all of the answers will be used.
-____________: Another name for dipolar molecules.

A)L amino acids
B)water
C)protons
D)zwitterions
E)leucine
F)serine
G)tyrosine
H)cysteine
I)glutamate
J)histidine
K)proline
L)asparagine
M)D amino acids