伦敦的交通是什么样子的？
A Compared to Beijing, what’s the traffic like in London?
A 和北京比较起来，伦敦的交通是什么样子的？
B In London? It’s getting better in London. Drivers have to pay if they go into the city centre. So there’s less traffic now and less pollution.
B 在伦敦？它现在比原来要好多了。司机要交纳通行税才能进市中心。所以现在交通比较好，污染也在减轻。
A Drivers have to pay! That might be a good idea for Beijing.
A 司机要交钱！这个会是个好主意，如果它能在北京实行。
当你必须，一定要做某件事时，你可以说must . . 一定 或者 have to . . / 必须 . .
练习：
You must be careful when you drive.
You have to be 18 to drive.
You must get a visa to visit China. 你一定要小心开车。
你必须等到18岁后才能开车。
你一定要拿到签证才能去中国。