The young man stopped and looked back as if ______ whether he was being followed.
-Do you like ___ here? -Oh,yes. The air,the weather,the way of life. Everything is so nice.
I like ____ in the autumn when the weather is clear and bright.
It was at four o'clock in the afternoon ____ he and his grandpa reached the museum in Guanghan.
I consider____ my duty to help you.
Is_possible to fly to the moon in a spaceship?