在基站选点时，天线摆在何处最好。（）A、越高越好 B、越低越好 C、无所谓 D、要根

设a=0.9²，b=2^0.9，c=log₂0.9，则a，b，c由大到小的顺序为 ______．

Mark _____ have hurried. After driving at top speed, he arrived half an hour early. [ ]

A. needn't

B. wouldn't

C. mustn't

D. couldn't

B型超声(BUS)对哪种结石诊断准确率高

A．胆囊结石
B．胆总管结石
C．肾结石
D．肝内胆管结石
E．胰腺结石