amphoterism of methanol
Compound A is much more basic than compound B (charge effect). By the element effect, C is much more basic than A; this follows from the fact that if we rank their conjugate acids, the conjugate acid of C, ammonia, is less acidic than the conjugate acid of A, CH3OH. Note that a comparison of A and B brings into play the amphoterism of methanol: like water, it can act as both an acid and a base in disimilar reactions.