If we want ______much cleaner world, we should reduce _______ emission of carbon dioxide.
| A．a; a | B．a; / | C．a; the | D．the; / |
I'm soto all those volunteers because they helped my terrible day end happily.
| A． | special | B． | superior | C． | grateful | D． | attractive |
A ship in harbor is safe, but that’s not ______ ships are built for.
| A．what | B．whom | C．why | D．when |
Just as I got to the school gate, I realised I ______ my bank in the cafe.
| A．have left | B．had left |
| C．would leave | D．was leaving |
scientists have learned a lot about the universe, there is much we still don't know.
| A． | Once | B． | Since | C． | Though | D． | Unless |
If you come to visit China, you willa culture of amazing depth and variety.
| A． | develop | B． | create |
| C． | substitute | D． | experience |