certain形容词表语形式

往往用于It is certain that…句式中，例如：

1、It is certain that Rodney arrived the previous day.罗德尼肯定是头天到的。

2、Their seating arrangements are unknown ， but it is certain that they were arranged in a certain order.其座次的顺序尚不得而知，但肯定是有区别的。