Should any of this material be introduced into a sanitary sewer system,请问这是一个什么语法现象.
问题描述：
Should any of this material be introduced into a sanitary sewer system,请问这是一个什么语法现象.
全句如下：
Should any of this material be introduced into a sanitary sewer system,flush
with copious amounts of water.
答
虚拟语气,从句省略if,将should前置倒装.
如此物质被引入至卫生下水道系统,则以大量水冲洗