Which of the following statements is an identifying characteristic of a mixture?
a. a mixture must have a definite composition by weight
b. a mixture can consist of a single element
c. a mixture must be homogeneous
d. a mixture can be separated by physical means

Ithink the answer is a

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.