题目

----- __________it be Li Ping who broke the glass? ---- No. It __________ be Wu Dong who did it. A. Could; may     B. Can; must      C. May; must      D. Can; can 答案：B 解析: 略在浏览动物园时，常常能听到它们的叫声．老虎吼叫声的频率低低，而猴子戏耍的叫声频率高高（填“高”或“低”）．