What is the name of the act that limits the president's ability to keep troops around the world?

The 1973 War Powers Resolution, which is the name of the Act that you are trying to identify.  Congress (both Senate and House) voted it into law OVERRIDING President Nixon's Presidential Veto.  This act was passed to clarify and remove doubt that Congress and NOT the President had the right and the responsibility to send American troops to War.  It legally limits and clarifies the presidential reach, overreach, and authority and some argued and thought it necessary because the President is also the Commander-in-Chief and Directs all branches of the military and there is the presupposition of a conflict of interest.  Also, in America, no ONE person can declare WAR - ONLY the legally elected representatives of the people of this nation can declare War and they must do it as a majority body.

4.a depression is the answer