The pregnant woman always sits in the non-smoking area of restaurants to reduce her exposure ________ smoke.

It’s the fourth time that heavy smog(雾霾) has hit the city this month— It’s high time we _______ measures to fight air pollution

I’m in the afternoon. We can discuss the plan for our summer vacation then.

_____ does your mother usually go to the office —By bus.

Kate，what’s your favourite subject–___________.We can learn more about the world.