Apresident might persuade congress to pass a certain bill by

The choices can be found elsewhere and as follows:

threatening to veto other bills Congress is eager to see enacted

withholding congressionally appropriated funds for federal projects in the home districts of uncooperative legislators

appealing to the Supreme Court for support
   
all of these methods are ways a president can pressure Congress

I believe the answer is the first option. A president might persuade Congress to pass a certain bill by threatening to veto other bills Congress is eager to see enacted 

The answer would be political systems .