In an embryo, the tissues that receive a nerve produce sprouting
factor, which encourages nerves to grow and branch, while
the nerve produces anti-sprouting factor, which inhibits nerve
growth. this is an example of a. a positive feedback system
b. a negative feedback system c. thermoregulation
d. homeostasis.

Which of the following statements is a scientific claim? a. the early solar system had large amounts of water; so, the oldest objects in the solar system should also be abundant in water. b. earth is shaped like a sphere even if not all of the scientific observations related to its shape support this idea. c. the mass of the universe is much greater than current models predict; it is not possible to explain this inconsistency. d. planet earth is abundant in water, but there is no way to scientifically determine from where earth's water originated.