Removal of hydrogen and addition of hydrogen are associated with which processes, respectively?

Correct answer: Oxidation and reduction

In the hydrogen-based definitions of redox chemistry, removal of hydrogen from a substance is oxidation, while addition of hydrogen is reduction. Thus the required order is oxidation followed by reduction, so option A is correct. Option B reverses the two processes. Precipitation, decomposition, combination, and displacement describe other reaction patterns and do not define the gain or loss of hydrogen in this context.