Answer: It is A
Explanation: C and D are jokes/ complete lies. B is wrong because Darwin did observe that animals and plants adapted (evolved) to suit their environments.
I want to Say A - I searched google and it said that Archaea has something called membrane lipid bonding, ( which is oils and fat ) I didn't see anything about nucleus, size, or cell wall.
Hope this helped!
the answer is a it can be used as an energy source by organisms