The amount of sand in soil is changed and the drainage time is measured. Which is the dependent variable?

Correct answer: Drainage time

The direct answer is B: drainage time. The amount of sand is deliberately changed, so it is the independent variable. The time taken for water to drain is then measured and may change because of that sand amount; it is therefore the dependent variable. A is wrong because it is the manipulated input, not the measured result. C is a sensible controlled variable: starting water volume should normally be the same so the comparison is fair. D, total soil mass, may also need control or careful definition, but it is not the requested measured outcome. Follow the chain: change sand amount, pour equal water, measure drainage time. The final measurement is dependent. Memory cue: the result that responds is dependent.