A．It urges campers to treat its service with respect.
B．It urges campers to love the nature.
C．It shows respect to the nature.
D．It requires the campers to be clean in outdoor place.
A．St. John's University.
B．Massachusetts Institute of Technology.
C．University of California, Berkeley.
D．Yale University.
A．About 116 schools around the world now offer course materials free online to the public.
B．Open Course Ware only offers materials from graduate courses.
C．Visitors can learn the same things M.I.T. students learn, and they can receive credits toward a degree.
D．There are more visitors of the site from outside the United States and Canada.