Since optical paths are reversible, the opposite arrangement is also true.因为光路是可逆的, 所以也可以反过来安装.Her class teacher made a special arrangement to discuss her progress at school once a month.她班上的老师作了特别安排，每月讨论一次她在学业上的进展情况。Cop...
Most of them just stared at her in perplexity.他们多数人茫然地凝视着她。She looked at us in some perplexity.她有点困惑不解地看着我们.He scratched his head in perplexity.他困窘得直抓头皮....