What two-letter symbol stands for a medical prescription?

In 1835, two men in what is now which country patented the tuba? Which acclaimed 1994 documentary followed two Chicago high school basketball players chasing NBA careers? Which actor, who died in January 2009, was famous for playing Khan in "Star Trek" and Mr. Roarke on "Fantasy Island"? What word means two individuals or units regarded as a pair? In which U.S. territory did two locomotives meet for the 1869 "golden spike" ceremony completing the first transcontine… New York's two major airports, JFK and LaGuardia, both lie on which island? Which two boxers named Sugar Ray won world welterweight titles, one in 1946 and the other in 1979? Karl Ferdinand Braun shared the 1909 Nobel Prize in Physics for work on wireless telegraphy with which Italian?