Aneurotransmitter is best described as:
a. a molecule that allows one cell to communicate with other cells.
b. a molecule that initiates a signaling cascade in response to hormone binding on a cell membrane receptor and activating a g protein.
c. a hormone that binds to a cell membrane hormone receptor and triggers activation of another messenger system.
d. a chemical messenger released from synaptic terminals across synapses

The correct answer is D. A neurotransmitter is best described as a chemical messenger released from synaptic terminals across synapses.

Explanation:

A neurotransmitter is a biomolecule that allows neurotransmission, that is, the transmission of information from a neuron (a type of nervous system cell) to another neuron, a muscle cell or a gland, by the synapse that separates them. The neurotransmitter is released from the synaptic vesicles at the limb of the presynaptic neuron, to the synapse, crosses the synaptic space and acts on the specific cell receptors of the target cell.

substitution is the answer in this case

the fossil record provides evidence of a common ancestor to many species.