A student asks how container width affects the time taken for water to evaporate. Which factor should be measured?

Correct answer: Time taken for evaporation

The question asks how container width affects the time required for water to evaporate. The factor being deliberately changed is container width, so it is the independent variable. The response to that change is the time taken for evaporation, which must be measured. This response is the dependent variable because its value may depend on the width of the container.

Option B is correct because the investigation records evaporation time as its outcome. To make the comparison fair, factors such as the amount of water, temperature, airflow, and starting conditions should be kept as similar as possible. Option A is the independent variable, not the measured result. Water colour and room decoration do not answer the scientific question and should not be treated as the outcome.