It occurs in many mammals besides humans; a prominent example is porcupines, which raise their quills when threatened
Temperature affects the plants because if its too cold a plant would not grow.
Copulation is animal sexual behavior in which a male introduces sperm into the female's body, especially directly into her reproductive tract.
I think that i grows for about 1 month
D. Membrane. Can also be called cell membrane so you don't get confused with the nucleus's membrane/envelope!
