It is the test system, _____ the teachers, that is to blame for the heavy burden(负担)of middle school students nowadays.
—Did you attend David’s wedding last night? —No. I ________ before that.
The man showed us so heavy a stone _______ no man can lift.
To improve your reading ability, you should ____ half an hour every day for learning new vocabulary.
This disaster ______ that people had no knowledge of first aid and they hadn’t known how to protect them-selves in face of danger.
I just wonder ____ that delights the whole family so much.