题目： 碱式滴定管如何试漏？ 答案： 参考答案：装蒸馏水至一定刻线，直立滴定管约2min，仔细观察刻线崐上的液面是否下降，或滴定管下端尖嘴上有无水滴滴下，如有漏水，则应调换胶管中玻璃珠，选择一个大小合适比较圆滑的配上再试，玻璃珠太小或不圆滑都可能漏水，太大操作不方便。
题型：选择题 My sister _____ the League last month and she has decided to _____ the activity to help the aged next week. [ ]A. joined; join in B. joined in; join C. joined; join D. joined in; join in 查看答案
