发生率最高的原发性免疫缺陷病是
A．细胞免疫缺陷B．体液免疫缺陷C．联合免疫缺陷D．吞噬细胞缺乏E．中性粒细胞缺乏
参考答案：B
按要求转换下列句型。
1. The blue skirt is my friend's. (对划线部分提问)
_____ _____the blue skirt?
2. Your mother is a teacher. (用a worker 改为选择疑问句)
_____your mother a teacher _____a worker?
3. Can't you see its name? (作肯定回答)
_____, I_____.
4. You can put the books on the desk. (改为祈使句)
_____the books on the desk,______.
5. Jim is a friend of mine. (改为同义句)
Jim is _____of _____ _____.
离心泵启泵前需要排空的原因是（）
A、避免启泵过程中电机振动过大
B、保护机械密封
C、避免流量瞬间过大
D、避免造成泵的气缚
