滴定管在装入滴定液之前，应该用滴定液洗涤滴定管3次，其目的是为了（），以确保滴定液（）。
参考答案：除去管内残存水份；浓度不变
Peter _____ the papers he was marking and reached for his cigarettes and matches. [ ]
A. set out
B. set off
C. set in
D. set aside
元气
