急性呼吸窘迫综合征时可采用 （）
A.高压氧舱
B.面罩吸氧
C.呼气末正压
D.持续低流量吸氧
E.间断高流量吸氧
参考答案：C
下列哪个地球数据是正确的（ ）
A．地球最大周长约为4万千米
B．地球表面积约5.1万平方千米
C．地球半径平均半径是6371米
D．以上数据都正确
He had studied hard, he would have been able to pass the exam.
A．He had studied harder
B．If only he studied more
C．Had he studied harder
D．When he studied more
