An increasing number of colleges and universities are offering research internships to high school students to provide them hands-on experience conducting research. In particular, biomedical research institutes run for about eight to ten weeks and require students to assist scientists with a long-term research project. These institutes offer rigorous training that will prepare high school students for demanding scientific study in a postsecondary setting. In the underlined portion, the writer wants to show that such institutes are more challenging than high school summer programs. Which choice best accomplishes this goal?