Large office buildings are often as big as small towns．They have their own trains，buses，and shops．Such buildings can be found in most cities around the world．When it was built，however，in 1943，the Pentagon（五角大樓）was the world's largest office building．It is，still many years later，among the largest．

The Pentagon is different from all other office buildings，however，because it is used by only one organization．This is the United States Defense Department，the headquarters（HQ）of the United States military--the army，the navy，and the airforce．When people think of the military strength of the USA，they usually think of the Pentagon．

The Pentagon was built across the Potomac River from Washington，DC，during the second World War．It took only two years to build in spite of its huge size．

Built in the shape of a pentagon--a five-sided figure--the building consists of five circles，divided into ten sections．Each side of outside pentagon is about 300 meters long．In the centre，there is a large space open to the sky．

Six stories high，the Pentagon has a total floor space of about two million square meters．Around it，there are about 45 kilometers of roads that are part of the building，and inside the building itself there are over 25 kilometers of passages．In spite of its great size，however，no office is more than a six-minute walk from any other office in the building．

Thirteen thousand people worked on building the Pentagon，and about thirteen thousand now work in it for the Defense Department．It cost 80 million dollars to build in 1943-a huge sum at that time，and one that many Americans thought it was too much．However，if the Defense Department had to rent such a building now，it would cost it around $30 million a day! The building was，therefore，a bargain．

1．This passage mainly talks about _________．

A．the large office buildings                           B．the army，the navy，and the airforce

C．the Defense Department of the USA             D．the Pentagon

2．The Americans built the Pentagon _________．

A．during the Second World War                   B．with ten sides

C．without a roof                                                  D．in the shape of a circle

3．Although the Pentagon is large，it _________．

A．only has seven stories                                 B．has only 45 kilometers of roads

C．is only a short walk between all offices         D．takes a long time to travel around it

4．Which of the following is TRUE?

A．The Pentagon costs $30 million to rent a day．

B．The Pentagon doesn't employ many workers．

C．The Pentagon is rented to the Defense Department．

D．The Pentagon cost an enormous amount of money at that time．

5．From the passage we learn _________．

A．the Pentagon is the largest office building in the world

B．the Pentagon is the headquarters of the United States military forces

C．there are 250 kilometers of passages in the Pentagon

D．compared with today's buildings，the Pentagon was very expensive to build