In a controlled experiment, the variable that is changed to test the hypothesis is called the: a. dependent variable b. independent variable c. responsive variable d. controlled variable

The variable that is intentionally manipulated or changed in a controlled experiment is know as the B) Independent Variable.

This is done, as the question states, to test the hypothesis. In other words, it is changed in order to see what results are produced, then the results are analyzed, and ideally an explanation of the changing results will arise and progress can be made in the experiment.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.

any abiotic or biotic factor in an ecosystem that causes a population's size to slow or decrease is a limiting factor.