机翼扰流片的主要作用是（）
A.减小阻力
B.减小着陆速度
C.减小机翼升力
参考答案：C
－How are you your classmates?
－Very well. I have made many friends here.
A．getting over
B．getting through
C．getting along with
D．getting on
水磨石若有返浆、杂质的缺陷时，合格品的外观质量缺陷规定：长×宽≤10mm×10mm的缺口不超过( )处。
A．2B．3C．4D．5
