Whats the only mammal that can fly backwards?

There are no mammals that can fly backwards. However, if you mean birds, then the humming bird is the only bird that is capable of reverse flight.

Hummingbird because of its wings(fast rate)

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.