Help please Why do scientists believe the universe is expanding?
The Doppler effect shows stars with red shifted light.
The Doppler effect shows stars with yellow shifted light.
The Doppler effect shows stars with green shifted light.
The Doppler effect shows stars with blue shifted light.

Which of the following is true for the actual yield of a reaction? it is always calculated as a ratio. it is the yield from the excess reactant. it is the yield from the limiting reactant. it is always less than the theoretical yield.

What method(s) do plants use to obtain nitrogen? select all that apply. absorb it from the atmosphere use bacteria to convert nitrogen to usable form obtain usable nitrogen compounds from the soil absorb nitrogen from water taken in at the roots

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.