Tibet is among the most popular places for Chinese tourists．The number of travelers of Tibet has grown by 10% every year for a few years．Since July 1，2006，when the first train ran 1956kilometers from Xining to Lhasa，more and more people have been going to Tibet．

The train stops at several famous places along the way，such as Qinghai Lake，Kunlun Mountain，and the Potala Palace．Passengers can also enjoy many activities during the journey，like Tibetan dancing and Karaoke．

On the train，passengers can have tea，eggs and noodles for breakfast，and fried chicken and green vegetables for lunch and dinner．Unlike most Chinese trains which have open-hole toilets，this one has special toilets which can collect the waste．There is also a special rubbish system （系统） in the train that keeps the environment clean．All the windows on the train can protect people from the bright sunlight．TV and electrical sockets （插座） for computers and mobile phones can be found on the train．

Because there isn't much oxygen there，trains will have oxygen masks （氧气罩） for those who needthem．It makes passengers feel more comfortable when they have enough oxygen on the famous"roof of the world"．There are also doctors on the train to make sure that all of the travelers are safe．

54．Which of the following is not among the places of interest？___

A．Qinghai Lake

B．Karaoke．

C．Kunlun Mountain．

D．The Potala Palace．

55．The underlined word"them"in the last paragraph refers to___．

A．oxygen masks

B．doctors

C．oxygen

D．passengers

56．What's the best title of the passage？___

A．Tibet-roof of the world

B．Magic train to magic Tibet

C．Beautiful views in Tibet

D．A comfortable trip to Tibet．