Pyridine Is a Weaker Base Than Aliphatic Tertiary Amines Because $\pi$

Pyridine is a weaker base than aliphatic tertiary amines because

A) the N is sp² hybridized in pyridine and sp³ hybridized in aliphatic amines.
B) there are no unshared electrons on the N in pyridine.
C) the electrons on the N in pyridine are delocalized around the ring.
D) the N in pyridine is already protonated.
E) the unshared electron pair on N in pyridine is part of the aromatic $\pi$ system.