Final answer:
The null hypothesis in experimental study is formulated to provide a statement that there is no effect or difference, which researchers test against to see if there is sufficient evidence to support the alternative hypothesis, without claiming absolute proof.
Step-by-step explanation:
Researchers formulate a null hypothesis in addition to a hypothesis when designing an experimental study because it specifies what they should observe when the hypothesis being tested isn't correct. The purpose of a null hypothesis (option C) is to formally state that there is no effect or no difference in an experiment, setting a baseline expectation that any observed effect is due to chance. When researchers conduct an experiment, they test both the main hypothesis and the null hypothesis.
Importantly, if we reject the null hypothesis, then we can assume there is enough evidence to support the alternative hypothesis. However, even when a null hypothesis is rejected, we should never claim that a hypothesis is proven true or false. Rather, we understand that hypothesis testing is based on probability laws, indicating non-absolute certainties.