Answer:
G proteins. (Ans. B)
Step-by-step explanation:
Metabotropic receptors are also called neurotransmitter receptor, they are indirectly linked with ions channels through the signal introductions mechanism on the plasma membrane of the cell & activating G-proteins. The Metabotropic receptor is activated by specific neurotransmitters (is known as a chemical messenger which delivers a signal across a chemical synapse, from 1 nerve cell to another target neuron).
G protein which is also called guanine nucleotide-binding proteins, that behaves as molecular switches inside the cells & they are involved in delivering the signals from stimuli outside the cell to its inside.