关于涡扇发动机产生的推力，下列说法正确的是（）。

Pitch is the movement of the aircraft about the （ ） axis.

（ ） is the movement of the aircraft about the longitudinal axis.

Which of the following statements is not true?

During the course of a flight, the （ ） will be a factor for the variation of the airplane’s weight.

Which of the following is not true?

Flaps increase lift by （ ） ．

Which word is not used in describing the shapes of the wing?

V2 is defined as the （ ） .

Which of the following is not true?

If the airplane has fixed landing gear, it is considered to be in a clean configuration when the （ ） ．