1£®Something must be done to prevent factories sending out poisonous (poison) gases so as to keep the city from being polluted.

2£®Despite the health problem caused by his excess weight, the wealthy businessman was still obsessed with making as much money as possible.

3£®It was not until the early 18th century that the significance of the event was generally realized.

4£®The fog was so heavy this morning that drivers could hardly make out the things just ten meters away.