Question

In an oxidation-reduction reaction, _________.
A.substances that give up electrons are reduced
B.both substances gain electrons
C.both substances lose electrons
D.one substance gains electrons, the other loses electrons

Answer 1

Oxidation is giving up of electrons and reduction is addition of electrons, so in an oxidation-reduction (redox) reaction both the phenomena occur.

Answer 2

Well you can rule out B and C immediately, because B requires electrons to appear from nowhere, and C requires electrons to vanish into thin air. If electrons are transferred at all, then D must be true. The only question is then whether A is true, too, and in fact it is not, since LEO the lion goes GER (Loss Electrons = Oxidation, Gain Electrons = Reduction) or OIL RIG (Oxidation Is Loss, Reduction Is Gain), or whatever your favorite mnemonic is.