The Correct Answer Is "A - Solar Day"
When cells communicate by the signaling process, one cell produces a signaling molecule that must be received by the signal receptor on or in the responding cell. Signaling molecules are often called ligands, a general term for molecules that bind specifically to other molecules (such as receptors).
Explanation:
A.They filter waste and extra water from blood so they can create urine, which is removed from the body.
