根据掩护者的人数、移动路线、方法和变化，将掩护分为：（）。
A、定位掩护
B、反掩护
C、假掩护
D、连续掩护
参考答案：A, B, C, D
The teacher ____ the office for a few minutes when we arrived. We didn't meet him. [ ]
A. had left
B. had left
C. has been away from
D. had been away from
肾病综合征患儿，禁盐两个月，近三天频繁呕吐，水肿未消退，嗜睡，血压下降，惊厥二次，诊断可能为
A．肾病综合征伴病毒性脑炎
B．肾病综合征伴急性胃肠炎
C．肾病综合征伴低钙惊厥
D．肾病综合征伴低钠血症
E．肾病综合征伴低钾血症
