[单项选择]Passage Five A wind tunnel is used for testing planes or plane models. In a wind tunnel air is blown over a plane or a model placed in a test section. Wind tunnel test sections are different in size depending on airflow speed requirements. Some low-speed tunnels have test sections large enough for a complete small plane. In the very high speed tunnels used for space testing, however, the model may be as small as a pencil. There are two ways of feeding air to the test section. In the constant flow tunnel, airflow produced by electric fans is forced through the tunnel to the test section, then through another tunnel section back to the starting point for reuse. The other way involves storing high-pressure air in a box, sending it out by a controlling device to pass through the tunnel and test section into another box. This way is usually used for a very short period of high-speed airflow. Wind tunnels are usually used to test planes before they are flown. Problems in a plane
A. they are used for large planes
B. they can produce a stronger wind
C. they are built to conduct a high-speed test
D. the air in them flows at a lower speed

[单项选择]Passage Five A wind tunnel is used for testing planes or plane models. In a wind tunnel air is blown over a plane or a model placed in a test section. Wind tunnel test sections are different in size depending on airflow speed requirements. Some low-speed tunnels have test sections large enough for a complete small plane. In the very high speed tunnels used for space testing, however, the model may be as small as a pencil. There are two ways of feeding air to the test section. In the constant flow tunnel, airflow produced by electric fans is forced through the tunnel to the test section, then through another tunnel section back to the starting point for reuse. The other way involves storing high-pressure air in a box, sending it out by a controlling device to pass through the tunnel and test section into another box. This way is usually used for a very short period of high-speed airflow. Wind tunnels are usually used to test planes before they are flown. Problems in a plane
A. it costs a lot to test a plane
B. the wings are not good enough
C. some problems are found with a plane
D. the wings meet the high-speed air flow in the tunnel

[填空题]Wind power are being used to generate (electronic)（）.

[填空题]Book Five

[填空题]Article Five: