A visit to NASA Langley Research Center would be very exciting. You could meet NASA scientists and engineers working with wind tunnels.
Wind tunnels are basically tubes through which air—or a gas—is moved to make “wind” in the tube. This “wind” moves past objects such as airplanes or just parts from airplanes.
It s always a good idea to test a new aircraft design in a wind tunnel before you build the real aircraft. Models tested in wind tunnels will always go through design changes before engineers are satisfied with its design and test results.
Wind tunnels are constructed with some very wide sections as well as some sections much smaller in size. An “open return wind tunnel”is open at both ends of the tube. It is usually largest at one end of the tube where you may even see the fan blade(风扇片)that creates the wind. This tube gets smaller as you move away from the fan blade. The tube begins to straighten in the next part of the wind tunnel called the Test Section. This is where you place the model for testing. The tube widens again as you move away from the Test Section.
Another wind tunnel is the “closed return” design. This tunnel is completely contained inside a building. The tunnel moves in a “loop” inside the building. A fan is located in the tunnel on one side of the building and the test model is located in the tunnel's Test Section on the other side of the building.
NASCAR race teams even test their race cars in wind tunnels to test and improve a car's design. These teams work hard to reduce a car's drag. In less than 150 years, wind tunnels have allowed mankind to improve cars on the ground, aircraft in the atmosphere, and spacecrafts in space. We can only imagine what will happen with wind tunnels during the next hundred years.
What could be the best title of the passage?

A．What Are Wind Tunnels Made of?

B．What Is a Wind Tunnel and How It Works?

C．Where Can Wind Tunnels Be Found?

D．Why Are Wind Tunnels Used?

Which of the following is the right shape of an “open return wind tunnel”？


In the “close return” wind tunnel, the fan is fixed________.

A．in the Test Section on the other side of the building

B．next to the models in the building

C．at one end of the opening

D．on the other side of the Test Section

By reducing a race car's drag, ________.

A．the car will becomes lighter

B．the car will be easy to operate

C．the car will move faster

D．the car will look more beautiful