作出由点光源S发出的光线,经平面镜反射后经过P点的光线.
先通过平面镜作出发光点S的对称点S′,连接S′P交平面镜于点O,OP为反射光线,SO为入射光线,如图所示:
— Will you please stay here for the party?
— Sorry, I _____. I'll have to go to an important meeting. [ ]
A. mustn't
B. needn't
C. can't
D. won't
运用参与式培训方法有哪些需要注意的地方?