The executive branch must receive approval from when appointing heads of executive departments, ambassadors, and federal court judges.
a. the house of representatives
c. the supreme court
b. the senate
d. federal bureaucrats

The answer is letter C. The Senate.
  The Executive branch must receive approval from  the Senate when appointing heads of executive departments, ambassadors, and Federal Court Judges.
  Depending on the country, the Senate constitutes the senators who may be appointed, elected or have inherited the title or acquired membership by other ways. The senate is usually related to the term as chamber of a bicameral legislature and is often called the upper house. The senate belongs to the legislative branch of a government who is responsible in the making of laws.