Dr. Xie and his wife, Dr. Cai, and Dr. Zhengzhou, the head of the Anesthesiology Department, have gathered for a picnic. They are joined by Dr. Bai, the wife of Dr. Gong, and the sister of Drs. Cai and Zhengzhou. They have come to eat a good meal and have a good time. Dr. Xu, the chief of Obstetrics and Gynecology, is also there, and he welcomes everyone to the picnic. He invites everyone to sit down and enjoy the food. He also invites the couple to sit by the side of the room and watch the cooking. They do