The correct answer is "Person attributes his own unacceptable thoughts or actions onto others." This defense mechanism, known as projection, occurs when an individual unconsciously attributes their own undesirable thoughts, feelings, or behaviors onto someone else. By doing so, they can avoid acknowledging or taking responsibility for these aspects of themselves, which helps to keep anxiety at bay. Projection is considered one of the most fundamental defense mechanisms and is often accompanied by repression, where the individual pushes the anxiety-provoking thoughts or experiences out of their conscious awareness.