He ____ people to love each other. [ ]
A. taught
B. teach
C. teaching
A
起飞、着陆哪些意外事件必须报告机长()
A.客舱烟雾
B.火警
C.旅客疾病/受伤
D.旅客调换座位
表面加工方法选择时考虑的因素?