题干

关于物体做曲线运动,下列说法中,正确的是(  )

A:物体做曲线运动时所受的合外力一定不为零

B:物体所受的合外力不为零时一定做曲线运动

C:曲线运动的加速度一定是变化的

D:物体只可能在变力的作用下做曲线运动

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A

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    Spend any time in London, England's capital, and you'll quickly gather that it's a multicultural (多元文化的) community. Look around at your fellow passengers on the Tube(地铁)or the bus. They're of every skin color and dress differently to one another. Listen, and you'll hear many other languages besides English spoken. Some of these people, no doubt, will be tourists who are in London to see the sights. But others – in fact probably most – will be living their lives there, along with millions of others.

    Along with white British people, there are Britons from, or with parents and grandparents from, the Caribbean, India, China and most other places. This makes London a fascinating place in which to live. The reason is that when people settle in a place, they don't just buy a house and live there, but bring aspects of the culture of their “old country” with them.

    The most visible sign of this is the number of restaurants offering dishes from different parts of the world. In a city in which it's estimated 250 different languages are spoken, you can expect a similarly wide range of foods to be available. You would expect in one of the world's leading cities to encounter(遇到) French, Italian, Chinese and Indian eateries. But in London you'll also find Polish, Patagonian and Palestinian restaurants.

    However, London's multiculturalism isn't just about food. Many types of people are gathered in one space, but the way they live differently shows in that space. They worship(崇拜)differently, for one thing. Alongside the famous old English churches by Nicholas Hawksmoor and Christopher Wren – responsible for one of the capital's most famous landmark, St Paul's Cathedral—you'll find mosques(清真寺), temples and synagogues (犹太教堂).

      London even speaks its own special kind of English. Language experts created the term “Multicultural London English” to identify the dialect of English that appeared at the end of the last century.

    All of this makes London a very surprising and varied place to call your home. But, in a way, this has long been true. In the 18th century, the compiler(编纂者) of the first English dictionary, Samuel Johnson, once said: “ He who is tired of London is tired of life.”