Over the past half century, ________ chemical fertilizers has become very common in farming.
A. having usedB. useC. usedD. using
The problems are too complex ________ easily.
A. to be solvedB. to solveC. solvedD. solving
________ by the policeman, Ciara Judge gave some information.
A. AskingB. AskedC. To be askedD. Ask
With time ________ by, they got to know each other better.
A. passesB. passingC. passedD. to be passed
They did nothing but ________ silent.
A. to keepB. keepingC. keptD. keep
He was seen ________ football with his classmates there.
A. playB. to playC. playedD. being played
