腹部正位片发现右上腹部一圆形致密影,为了进一步明确诊断,最简单的首选方法是
A.B超检查
B.侧位子片检查
C.静脉尿路造影检查
D.CT检查
E.MRI检查
参考答案:B
A、B两列简谐波在某时刻的波形如图所示,经过t=TA时间(TA为波A的周期),两波再次出现如图波形,则两波的波速之比不可能的是( )
A.1:1
B.2:1
C.3:1
D.3:2
—Hi, Tom, Any idea where Jane is?
— She __ in the classroom. I saw her there just now.
A.shall be
B.should have been
C.must be
D.might have been