Questions 17-20 are based on the following passage. You now have 20 seconds to read the questions 17-20. Where is the second test carried out

A．In the air.
B．On the airfield.
C．Under water.
D．At the plane manufacturing factory.

Questions 17-20 are based on the following passage. You now have 20 seconds to read the questions 17-20. Where is the second test carried out 您的浏览器不支持 audio 元素。