The following question has a paragraph from which the last sentence has been deleted. From the given options, choose the one that completes the paragraph in the most appropriate way.

Research on animals is performed to gain more knowledge about diseases and how to cure them, and to evaluate drugs for toxicity before testing them on humans. In fact, animal studies have played a vital role in almost every major medical advance.Gaining useful knowledge from animal research requires robust experimental findings: different scientists should be able to reproduce them in different locations. _________________