He fell asleep immediately last night; he must ________ (be) very tired.
have been
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Howlong________they________(dig)theditch?
Onlywhenyouhaveobtainedsufficientdata________cometoasoundconclusion.
Only when you have obtained sufficient data ________ come to a sound conclusion.
Thisdiploma(毕业文凭)________thatyouhavecompletedhighschool.
________(fail)severaltimes,theyneedsomeencouragement.
