【单选题】There are twenty girls in the classroom. Some are cleaning the tables, and __ __ are sweeping the floor. [ ]
【简答题】A.Because some book in the library are very expensive. B.Because some books in the library are rare. C.Because sometimes students need certain materials urgently. D.Because some students won't return ...
【单选题】The students are doing the cleaning in their classroom. Some are cleaning the windows and the doors, _______ are sweeping the floor.
【简答题】仓库储存费用的构成中,( )是最难确定和测量的。