What role does the executive branch play in checking the power of congress?
a )it can declare war on foreign countries
b) the president may veto congressional legislation
c) congress can create federal courts and can impeachment judges
d) the president can decide that laws of congress are unconstitutional

The President has the power either to sign legislation into law or to veto bills enacted by Congress, although Congress may override a veto with a two-thirds vote of both houses. The Executive Branch conducts diplomacy with other nations, and the President has the power to negotiate and sign treaties, which also must be ratified by two-thirds of the Senate. The President can issue executive orders, which direct executive officers or clarify and further existing laws. The President also has unlimited power to extend pardons and clemencies for federal crimes, except in cases of impeachment.

So I think the answer is b. The President may veto Conressional legislation.