Final answer:
The president can act more unilaterally in setting foreign policy, utilizing formal powers granted by the Constitution, while Congress retains significant influence through various powers including oversight and budgetary authority.
Step-by-step explanation:
In regards to the president's role in setting foreign policy, option c, the president can act more unilaterally, is true. While the Constitution does give the president substantial formal authority in foreign policy, the president and Congress share power in this realm.
However, presidents have been able to use executive orders and executive agreements to act without immediate congressional approval, thus increasing their unilateral power. Decisions such as the deployment of military forces and the use of military force show the president's capacity for acting independently. Nonetheless, congressional involvement is still significant, as they possess amending, oversight, and budgetary powers, as well as constitutional powers related to appointments, treaties, and war.