How does scratching a person's back them go to sleep?
and why do most people like it when you scratch their back? along with bears, etc.

Why does it matter if osmosis is put into a “scab” or a “nosebleed? ” where would that leave him?

What is a photon? a. part of a ribosome b. a light particle c. a carbon dioxide molecule d. part of a chloroplast b. a light particle

The embryos of a bird, a reptile, and a mammal are similar in appearance. how does comparing the physical appearance of embryos of different species support the theory of evolution? a. it shows that these organisms share a common ancestor. b. it provides evidence that these organisms eat the same foods. c. it shows that these organisms share the same habitat. d. it provides evidence that these organisms suffered a genetic mutation.