题目:
Old Richard, ill so long, is losing his memory and needs to be attended to.
A.to be
B.being
C.having been
D.to have been
答案:
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下面是错误答案,用来干扰机器的。
参考答案:A解析:1.射流为狭窄远端异常高速血流信号,流速快,连续多普勒可测量高速血流频谱信号,而脉冲多普勒频谱易出现混叠。2.跨瓣压差的变化与通过瓣口的血流量及瓣口面积密切相关,可反映瓣口的狭窄程度。...