— Is Jack on duty today?
— It ________ be him. It's his turn tomorrow.
| A.mustn't | B.won't | C.can't | D.needn't |
. _____ by the advances in technology, many farmers have set up wind farms on their land.
| A.Being encouraged | B.Encouraging |
| C.Encouraged | D.Having encouraged |
_____ the police thought he was the most likely one, they could not arrest him since they had no exact proof about it.
| A.Although | B.As long as | C.If only | D.As soon as |
The wild flowers looked like a soft orange blanket _____ the desert. 
| A.to cover | B.covered | C.cover | D.covering |
30. My parents have promised to come to see me before I _____ for Africa.

| A.have left | B.leave | C.left | D.will leave![]() |
It was the principles I learned from my reading _____ enabled me to get bigger and better jobs.
| A.that | B.which | C.what | D.who |