Question

the president must stop doing something if the supreme court says it is unconstitutional. which arrow stands for this check?

Explanation:

The problem is about the system of checks and balances in the US government. The Supreme Court (Judicial branch) checking the President (Executive branch) for unconstitutionality means the arrow should go from Judicial to Executive, as the Judicial branch (Supreme Court) is checking the Executive branch (President) here.

Answer:

The arrow from the "Judicial" circle to the "Executive" circle (the arrow representing the Judicial branch's check on the Executive branch for constitutional compliance).