Question

a limitation on the presidents power to appoint ambassadors is that
the senate must approve them.
the house must approve them.
the house and senate must approve them.
the supreme court must approve them.

Explanation:

The U.S. Constitution (Article II, Section 2) states that the president has the power to appoint ambassadors, but this appointment is subject to the "advice and consent" of the Senate. This means the Senate must approve such appointments. The House of Representatives is not involved in the approval of ambassadorial appointments. The Supreme Court also does not have a role in approving these appointments.

Answer:

the Senate must approve them.