Forms of Radiation That Are Not Visible

Multiple Choice

Forms of radiation that are not visible

A) are,by definition,not part of scientific theories because they cannot be seen.
B) have been detected only since the 1970s.
C) probably hold great promise for the future,but we have not been able to make any scientific use of them with present technologies.
D) have allowed us to determine much of what we now know about the universe.