破伤风病人气管切开的主要指征是:()
A.呼吸中枢麻痹
B.肺部感染
C.抽搐频繁而不易用药物控制
D.胸腹肌强直,呼吸受限
E.吞咽困难
参考答案:C
某种火箭被竖直向上发射时,它的高度h(m)与时间t(s)的关系可以用公式h=-5t2+150t+10表示.经过______s,火箭达到它的最高点.
—Hello, Mike. Long time no see. Where are you?
—Oh, not only my parent but also I _______ Wuhan for a month.
A.have gone to
B.have been to
C.has been in
D.have been in