21. Barack Obama once again came to _________ power in November, 2012, becoming _________ 45th president of the United States.
A. 不填; 不填 B. the; the C. the; a D. 不填; the
22. --Rose, shall we attend the lecture about food and its nutrition this afternoon?
--_________? It is closely related to our health.
A. What if B. Why not C. How come D. What for
