Some practices in the last period of the DP government encouraged the military officers who were in search of a military intervention. Criticisms about the authoritarian rule of the government led some intellectuals to cooperate with the pro-junta groups in the army. 

The junta took control of the city centres, especially the capital city Ankara, in the morning of May 27th.

A special court which was called “the Supreme Court of Justice” was established.

Because the coup was not achieved in a chain of command, a serious confusion arose on managing the post-coup period. For this reason, the architects of the coup formed a commission which was called the National Unity Committee (Milli Birlik Komitesi).

After the coup, most of the high ranking military officers who had served in the DP government were retired.

Therefore, the correct option is D.