Most scientific questions are developed from Observations.
Answer:D. Compound.
Explanation:
A compound is defined as a pure substance: formed when two or more elements chemically combine to form bonds between their atoms.
An oxidation-reduction (redox<span>) </span>reaction<span> is a type of chemical </span>reaction<span> that involves a transfer of electrons between two species. An </span>oxidation<span>-reduction </span>reaction<span> is any chemical </span>reaction<span> in which the </span>oxidation<span> number of a molecule, atom, or ion changes by gaining or losing an electron</span>
