Is it constitutional to have an impeachment trial after a President has left office?

The correct answer is Yes.

Explanation:

Here is why! The impeachment vote for Former President, Donald J Trump, infact happened while the 45th president was in office. NOW! This means that the house is obliged to give it to the senate. While the Senate was not in session, and at the time Senate Majority leader McConnell, said he would not bring the senate back sooner, which means that the house couldn't send the articles. This means, that the House had the right to do it, when they could, and if Republicans felt the couldn't do that, they would have taken it to the Supreme Court.

hello your answer is d