The chloroplasts of flowering land plants typically contain at least two photosynthetic pigments, chlorophyll a and chlorophyll b, that differ in the wavelengths of light they absorb. The synthesis of chlorophyll pigments from precursor molecules is a process that involves many sequential enzyme-catalyzed steps. Researchers studied the growth and photosynthetic ability of a plant that contained a mutant form of one of the enzymes required for chlorophyll biosynthesis.

Q2) Identify an appropriate control that the researchers should use when they study the growth and photosynthetic ability of the plant with the mutant enzyme.