单项选择题

A new technique （）, the yields as a whole increased by 20 percent.

A. working out
B. having worked out
C. having been worked out
D. to have been worked out

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单项选择题
As teachers we should concern ourselves with what is said, not what we think （）.

A. ought to be said
B. must say
C. have to be said
D. need to say
单项选择题
The Managing Director said that improving relations with the association would not be easy, but that they （） to try.

A. would have decided
B. decide
C. have decided
D. had decided
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