We主语
are系动词
sure形容词充当表语
that we shall success宾语从句
有些形容词具有动词的含义,所以也可以带一个宾语从句；that可以省略.
例句：
I am sorry I am late.
I am glad that you can join us.
Are you sure his answer is right?
常用来引导宾语从句的形容词有：sure,certain,glad,please,happy,sorry,afraid,satisfied,surprised大神！您太厉害了！能帮到您是我的荣幸