The word "such" in Paragraph 2 refers to ______.

A．devices that enable astronauts to control their spacecraft
B．the value of the systems approach
C．practical applications of space research
D．ways of monitoring patients

A．Parents ought to send their children to college as a duty.
B．Parents should feel guilty if they are unable, for whatever the reason, to send their children to college.
C．If they can't afford, parents should take loans for their children to go to college.
D．Parents must support their children even after their marriage.