— should we clean the library?
—Twice a week．
A：How many
B：How much
C：How long
D：How often
货船运来1408吨煤，这些煤被装上火车运走，每节车皮(货运车厢)可装17.5吨．要有____节车皮才能把这些煤运走？
It will _____ cold in Harbin. （ ）
