The Particular Neurotransmitter Present at a Synapse

The particular neurotransmitter present at a synapse

A) indicates the subtype of G protein that will be coupled the receptor.
B) does not indicate the subtype of G protein or second messenger that will be coupled to the receptor.
C) indicates the second messenger that will be coupled to the receptor.
D) indicates the ion channels that will be targeted by second messengers.
E) indicates if the effect on the synapse will be excitatory or inhibitory.