B. smiling when you are happy
This is not an action that is controlled by the process of homeostasis in the body. Homeostasis is the process which is responsible for regulating the the internal environment of the body.
for instance, you go to the bathroom when your kidneys want to eliminate excess water and other substances.
Your lungs need more air when you are exercising so homeostasis is responsible of seeing that you get enough of it.
and sweating when you are hot to remove excess heat from your body via sweat.
These are all involuntary actions controlled by the process of homeostasis.
Smiling is a voluntary action. you do not need to smile. and you can whenever you like and not when you don't.
They're considered to be human like hands. They have a thumb like humans which allows them to grip onto trees and maneuver better. It also helps them with their grip onto branches and trees because they rarely come down from up there, so they need to be able to grip tightly even a sleep. I would say it's natural selection due to evolution.
Decreased birthrate can cause a slowed birth rate.
When this occurs the neutrons released by a fission reaction continue striking more nuclei. If the fuel rods in a reactor vessel produce too much heat, this condition may occur.
the earths crust because it is the first layer of the earth
