Mr. White together with his three colleagues __________ at the meeting last week.
________ reducing pullution, man should pay more attention to conserving energy.
I was too busy at that time, ________ I would have given you a hand.
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.