Reaction Intermediates Differ from Activated Complexes in That

Reaction intermediates differ from activated complexes in that

A) they are stable molecules with normal bonds and are frequently isolated.
B) they are molecules with normal bonds rather than partial bonds and can occasionally be isolated.
C) they are intermediate structures which have characteristics of both reactants and products.
D) they are unstable and can never be isolated.
E) all reactions involve reaction intermediates, but not all have activated complexes.