Our government has tried many ways to _________ the smog haze(雾霾) problem. Maybe we’ll have a clearer sky in the near future.

The American warships(军舰) have appeared near South China Sea Islands again.—We must let the Americans know clearly that the islands ______ China.

We must listen to the teacher ________ possible.

Our planet is about yearsold.

It is really fun to hike and I often gohiking in the forest.–But hiking alone in the forest ______ bevery dangerous.