We used to see each other ____ but haven't heard from him since last year.(2012 .辽宁)
I think you should go back to your plan, which is much more practical than the present one.
She has a gift for creating an atmosphere for her students ____allows them to communicate freely with each other.
___ not to miss the flight at 15:20, the manager set out for the airport in a hurry.
The lack of eco-friendly habits among the public is thought to be a major _____of global climate change.
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