Gerald Ford had difficulty being an effective president because of what?
A) he refused to keep Henry Kissinger on as secretary of state
B) Americans did not believe he had not been involved in Watergate
C) the Democratic Congress did not support his policies, and new limits had been imposed on presidential power
D) the Republican Congress refused to pass his far-reaching domestic programs
The best answer of the ones given here is clearly C. There are certainly other reasons why Ford had such a hard time during his presidency but none of these other reasons (other than C) is presented here.
In the wake of Watergate, new limits had been put on presidential power by Congress. Congress did not want another president to be able to run amuk the way Nixon had. Congress at that time was controlled by Democrats, not Republicans. For these reasons, C is the best answer.
However, a much more important reason for Ford's lack of success is that he was too closely linked to Nixon in the public eye. This made it hard for him to gain support among the people.