#1 is a trick question . . .
1) Let be the set of all U.S. presidents,
and let be the set of all ordered pairs
such that succeeded in office.
Is the graph of a function?
It is true that every President had a successor (well, except Dubya).
But Grover Cleveland served two nonconsecutive terms.
. . He was the 22nd President and was succeeded by Benjamin Harrison.
. . He was reelected as 24th President and was succeeded by William McKinley.
Hence, set contains: (Cleveland, Harrison) and (Cleveland, McKinley).
Therefore, is not a function.