Final answer:
Executive privilege is used to safeguard the confidentiality of presidential communications. This principle is not explicitly stated in the Constitution but has been recognized since the first presidency. The Supreme Court has ruled that it cannot be used to avoid legal proceedings. So, the correct answer is option e.
Step-by-step explanation:
The principle of executive privilege is primarily used to safeguard the confidentiality of presidential communications. This privilege is meant to ensure that a president can secure candid advice from advisors and staff without concern for public disclosure. This power, while not enumerated in the Constitution, has been recognized since George Washington's administration.
However, it was limited by the landmark United States v. Nixon Supreme Court case, which demonstrated that executive privilege is not absolute and cannot be used to avoid prosecution or civil suits. Despite these limits, the concept of executive privilege has expanded over time, alongside the broad interpretation of presidential powers in Article II of the Constitution. So, the correct answer is option e.