It was the fifth time that he ______ to such a meeting.
If we keep wasting so much energy, _____are that our oil wells will dry up and the environment will be destroyed.
— Where is my English book?— I brought it to you _____you were in hospital yesterday afternoon.
The nutrients in _____falls into the ocean quickly become available to other living creatures.
Don’t forget where the emergency exits are _____an emergency.
The lake is calm and clear, and one of the things that _____in the water is the famous tower.