What was the main point to the tenure of office act of 1867

The Tenure of Office Act of 1867 was an American federal law that regulated the dismissal of ministers from the Cabinet. It gained notoriety in particular through the impeachment proceedings against the President Andrew Johnson, who was accused of having violated it. In 1887, Congress rescinded the law. Later, in 1926, the Supreme Court invalidated a law similar to the Tenure of Office Act but which did not apply to Cabinet posts.

letter d is correct.