Which of the following explains why elements, such as carbon and nitrogen, are never permanently removed from the environment?
a. They are replenished by sunlight.
b. They are replaced by volcanic eruptions.
c. They are produced constantly by nutrients.
d. They are cycled through ecosystems.

50 pts plz what is the physical state of matter of baking soda.

An electron moved from shell n = 2 to shell n = 1. what most likely happened during the transition? a fraction of a photon was added. a photon of energy was absorbed. a fraction of a photon was removed. a photon of energy was released.

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.