超音速飞机在飞行速度超过1马赫时将穿过（）并产生（）。
A.声墙；涡流
B.声墙；气旋
C.音障；音波
D.音障；音爆
参考答案：D
诊断早期肺心病的主要根据是（）
A.心悸气促症状
B.肺动脉高压体征
C.慢性支气管炎病史
D.右心衰竭体征
E.肺气肿体征
Mark Twain presented the 19th-century America in his own unique way. Discuss Twain’s art of fiction: the setting, the language, and the characters, etc., based on his novel Adventures of Huckleberry Finn.
