Why is it important that a method being used to test a hypothesis is repeatable?

Which mantle is under the crust the upper mantle or the lower mantle i think it's upper let me know if i'm right

If the rna molecule in a human has the nucleotide sequence of guu, this would the amino acid valine would be needed to make the protein. how would this cha process was occurring in a mushroom?

Approximately what wavelength of light is best absorbed by chlorophyll a