Which are examples of negative feedback? Select three options.

a child whose thymus gland is building an immune system that gets stronger each day
when someone’s adrenal gland reacts to a scary movie by secreting hormones that make the heart beat quickly
when someone's pancreas stops producing the hormone that lowers blood sugar because the person hasn't eaten recently
when someone’s pancreas hormone increases every time they eat, but decreases when they aren’t eating
when a person takes calcium supplements so a gland will stop secreting a hormone that pulls calcium from the bones

Americium-241 undergoes fission to produce three neutrons per fission event. if a neutron-absorbing material is mixed in with this sample so that the rate of neutron production drops down to 1.8 neutrons per fission event, which will be effective at achieving a critical mass? check all that apply. remove a deflective shield surrounding the sample. remove absorbent material mixed in with the sample. compress the sample of americium-241.

Calculate the percent composition by mass of each element in al(oh)3. use at least three significant figures.

Steam reforming of methane ( ch4) produces "synthesis gas," a mixture of carbon monoxide gas and hydrogen gas, which is the starting point for many important industrial chemical syntheses. an industrial chemist studying this reaction fills a 1.5 l flask with 3.5 atm of methane gas and 1.3 atm of water vapor at 43.0°c. he then raises the temperature, and when the mixture has come to equilibrium measures the partial pressure of carbon monoxide gas to be 1 .0 atm. calculate the pressure equilibrium constant for the steam reforming of methane at the final temperature of the mixture. round your answer to 2 significant digits.