可控硅获得截止的条件是什么？
参考答案：
（l）阳极电位等于或小子阴极电位。（2）阳极电流减小至维持电流值以下。
Can you tell me_____________?
A．when did the train arrive
B．whether has the train arrived
C．when will the train arrive
D．whether the train has arrived
在环枕融合畸形的诊断中，MRI显示不佳的是（）
A.颈延髓交界处受压
B.颈延髓交界处变细
C.颈延髓交界处软化
D.环枕融合的骨性结构详细情况
E.扁桃体下移
