The chemical elements are arranged in order of increasing atomic number. Answer A.
It's a cyclohexane ring with an ethyl group at 1 and a methyl group at 3. The Ethyl group is bigger and more important group get's the first position.
1-ethyl-3-methylcyclohexane
Order, sensitivity or response to the environment, reproduction, growth and development, regulation, homeostasis, and energy processing.