terrible pollution!—Yes. We have to do something to protect our environment.

The shepherd had to round up the sheep ________ first night fell.[ ]

How are you feeling today—____ But I still cough very badly.

Earth is becoming more and more polluted. ______, people will move to Mars one day.

Young man, come off the grass; we forbid________ on the grass here. -Sorry, I didn’t notice it.