晶体三极管作共射组态时，其输入特性与二极管类似，但其输出特性较为复杂，可分为放大区外，还有（）区和（）区。
参考答案：截止；饱和
—I phoned you at 7:00 this morning. But there was no answer.
—Well, maybe I ____________morning exercises at that time. [ ]
A. was doing
B. did
C. is doing
D. would do
灌砂法测定土体密度试验中，使用的量砂必须符合（）。
A、粒径0.25-0.5mm
B、量砂始终处于干燥状态
C、量砂与空气的湿度达到平衡
D、每换一次量砂，都必须重新测定其密度
