Which of the following is an example of the principle of checks and balances?

A: Members of congress have the power to raise their own salaries.
B: Federal courts have the power to hear cases involving federal law
C: Presidents can appoint officers of the armed forces.
D: Presidents can veto an act of congress?

D: Presidents can veto an act of congress.

D: Presidents can veto an act of Congress is an example of the principle of checks and balances.

The principle of checks and balances is an important concept in the United States government that ensures no one branch of government becomes too powerful. It allows each branch to limit and control the actions of the other branches.

To determine which of the given options is an example of the principle of checks and balances, let's analyze each option:

A: Members of Congress have the power to raise their own salaries.
This option does not represent checks and balances, as it relates to the legislative branch controlling its own compensation rather than balancing the power of other branches.

B: Federal courts have the power to hear cases involving federal law.
This option represents checks and balances because it involves the judicial branch's authority to review and interpret federal laws, which serves as a check on the legislative and executive branches.

C: Presidents can appoint officers of the armed forces.
Although this option demonstrates the executive branch's power, it does not directly relate to the principle of checks and balances, which involves the separation of powers between the three branches.

D: Presidents can veto an act of Congress.
This option is an example of checks and balances as it shows the executive branch's power to reject or veto legislation passed by the legislative branch, maintaining a balance of power.

Therefore, the correct answer is D: Presidents can veto an act of Congress.