Why Can't Plants Use N2 Directly as a Nutrient

Why can't plants use N2 directly as a nutrient?

A) Plants lack the enzymes necessary to convert N2 into NO₃-or NH₄+.
B) Plants must use NO₃- to carry out nitrogen fixation.
C) N2 diffuses out of leaves as quickly as it diffuses in, so it has to be "fixed" to remain in leaves.
D) The N2 molecule is too large to enter the stomata.
E) Most soils are depleted of N2 as a nutrient.