Ok this is a big one! answer all of these and you get 20 points! hurry up and get the points btw make sure there right

Ok I know I'm not getting 20pts, but here r the answers:
17. C
18.A
19.D
20.A
21. can't see all answers, but is gravity. or gravitational pull

Neurotransmitters are messengers responsible for communication between neurons. they are released from synaptic vesicles and are received by receptors.  the communication is referred to as neurotransmission. the following statement is true about neurotransmitters: a. they're stored in synaptic vesicles in the axon.