Answer:When performing an experiment, the primary thing being tested is a hypothesis. This hypothesis is a testable statement that proposes a relationship between variables, often a cause-and-effect relationship. The experiment aims to gather data that either supports or refutes this hypothesis. Here's a more detailed explanation:Hypothesis:A hypothesis is a tentative explanation for an observation or phenomenon that can be tested through experimentation. Testing the Hypothesis:Experiments are designed to manipulate one or more variables (independent variables) to observe the effect on another variable (dependent variable). Gathering Evidence:The data collected during the experiment is analyzed to determine whether it supports or contradicts the initial hypothesis. Iteration:If the experiment doesn't support the hypothesis, it may lead to refining the hypothesis or designing a new experiment. Beyond Hypothesis Testing:While hypothesis testing is a core function of experiments, they can also be used to explore relationships between variables, answer "what-if" questions, or confirm previous findings.