You would use biuret reagent if you wanted to test an unknown sample for the presence of proteins, and a negative result would be a colored solution.

is this for the e2020 class

the relative standard reduction potential of the half-cell in which reduction occurs; more positive than the other half-cell. reduction is a chemical process in which electrons are added to an atom or an ion; it always occurs accompanied by oxidation of the reducing agent.

d. planting trees

the trees take in carbon to make oxygen.