Compared with 2 million tons last year, our coal output has increased _____three times; that is to say, our coal output has increased_____8 million tonsthis year.
It is a rule in his family that __________ comes home earlier should cook the dinner for the family.
The black horse is___________ of the pair.
I coutdn't have got to the meeting on time____________ an earlier train.
________ is quite natural,a beginner can't read the books written in English very quickly.
__________ it rain, the crops_____________.