I didn’t quite follow him because he explained the theory _____that is too abstract for me.
The question occurred to me ______ we were to get the machine needed.
— Was her concert a great success? — Sure. _______ such a good chance, how could she let it slip away?
______is now no doubt ________ global warming is a security threat to us all.
The doctors say that good diet, exercise and fresh air, all of which _____ the health and long life.
On farewell party the foreign teacher gratefully_____ all the helps from all the school.