The three phases of signal transduction is (1) reception, (2) transduction, and (3) response. Reception involves the binding of a ligand, may it be a hormone or a neurotransmitter; to a receptor, may it be a membrane receptor, cytosolic receptor, or a nuclear receptor. After binding of the ligand to the receptor, there will be signal transduction of events that will ultimately form a response. For instance, insulin actin on the insulin receptor will trigger a series of events that will increase the transcription of the gene translating for glucose transporters and ultimately, increase the number of glucose transporters embedded in the cell membrane leading to increased glucose uptake in tissues.
I would say that answer choice C is the best out of this selection. Carbon is the main element in organic compounds, and organic compounds just so happen to make up the cells that carry out life processes for all living things. Hope this helps.
