第25题: [单项选择]在IR序列中,射频脉冲激发的特征是( ) A. α<90° B. 90°—90° C. 90°—180° D. 90°—180°—180° E. 180°—90°—180° 参考答案:E
第26题: [单项选择]Questions 17-20 are based on a radio programme.
What is the purpose of building new houses facing north or south A. To avoid direct sunlight. B. To limit space used. C. To keep out the cold. D. To conform to other houses. 参考答案:A