Hello, jenjen!

#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 twononconsecutiveterms.

. . 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, isnota function.