浓度24%的盐水80克，加入______克水，含盐率为12%．
24%×80÷12%-80，
=160-80，
=80（克）．
故答案为：80．
维生素D缺乏性手足抽搐症典型症状中，喉痉挛主要见于（）
A.婴儿
B.1～2岁
C.2～3岁
D.学龄前儿童
E.学龄儿童
_____ the classroom, I found his pen lying on the ground. [ ]
A. When cleaned
B. If cleaned
C. When cleaning
D. If cleaning
