题目内容：

A new eight-kilometre road is under construction that links the port area with the motorway system. It is expected to carry 20,000 trucks and cars a day, which greatly reduces the overcrowded traffic in the center of the city. As part of the project, two four-kilometre road tunnels are being built below the central area of the city, one for traffic to the north and the other for traffic to the south .The two tunnels are about 20 metres below the surface and are 12 metres wide, providing for two lanes of traffic in each direction.

In the upper part of the tunnel two air-conditioning pipes remove the waste gas of trucks and cars and keep the quality of air inside the tunnel. The lighting is at the top of the tunnel, practically at its highest point. There will also be electronic signs at frequent intervals (间隔). They show traffic conditions ahead, and can be seen clearly by drivers. The wall is made up of four main elements, which include a waterproofing covering and , on the inside of the tunnel , a concrete lining (混凝土衬砌).

Each tunnel is roughly round and the lower part of the tunnel is somewhat flat .The surface of the road lies on the base, which is made of concrete and steel. The drainage system (排水系统), just below the road surface on one side, removes any extra liquid, particularly water. In the event of fire, the fire main, which is made of steel, pipes water to many fire hydrant stations at regular intervals along the length of the tunnel. The fire main is at the side of the tunnel, and at the level of the road surface. Other systems in the tunnel will include emergency phones .

1.Each of the tunnels under construction is ________.

A. eight kilometers long and twenty metres wide

B. four kilometers long and six metres wide

C. four kilometers long and twenty metres wide

D. eight kilometers long and six metres wide

2.Which part of the tunnel in the diagram is used to pipe out extra water?

A. 1    B. 3

C. 5    D. 6

3.Driving in the tunnel, one can know the traffic conditions ahead through ________.

A. the electronic signs    B. the lights

C. the trucks and cars    D. the emergency phones

4.The passage is mainly about ________.

A. the construction of a road    B. the design of a road

C. the construction of two tunnels    D. the design of two tunnels