A plant is placed at different distances and the amount it bends towards light is measured. What is the independent variable?

Correct answer: Distance from light source

Direct answer: Option A is correct. The independent variable is the factor deliberately changed to investigate its effect. Here the plant is placed at different distances from the light source, so distance is the independent variable. The amount by which the plant bends is measured and is therefore the dependent variable. Option A works because distance is the experimental input that changes from one trial to another. Option B is wrong as it is the measured response, not the deliberately changed factor. Option C is wrong because plant species should normally be kept the same to make a fair comparison, so it is a controlled variable. Option D is also normally controlled by giving plants equal water; it is not the factor being tested. The logical chain is: change distance → light conditions change → measure bending → compare results. Memory cue: ask “What did the investigator change?” The answer is the independent variable.