外语请问这句话should的用法和意思.
问题描述：
外语请问这句话should的用法和意思.
Should you fail the eyesight test you will be asked to produce a
satisfactory eyesight report issued by a general practitioner.
这里的should为什么在肯定句也可以放在前面,是什么用法来的?
答
虚拟语气为了强调可以采用此倒装形式,去掉if,将should提前.