What type of variable is the extension of a spring?

Correct answer: Dependent variable

The direct answer is D: dependent variable. Spring extension is the amount by which the spring length increases, usually measured after a load is applied or changed. The load is the cause or independent variable, while the extension is the response. Therefore the measured extension is dependent on the load. A would be the deliberately changed load, not the resulting length. B would be something kept fixed, such as the same spring. C means a quantity that remains unchanged, whereas extension is expected to change. The reasoning is: apply or vary load, observe and measure the increase in length; the observed effect is dependent. Memory cue: cause is independent, measured spring response is dependent.