they are ( ) very beautiful中间填什么?

可以填很多东西.比如否定词 not.表示“也”的 also.以及各种表示判断的副词.比如indeed,definitely,undoubtedly,等等.
还可以填各种插入语,比如：
They are (,in fact,) very beautiful.
They are (,in my opinion,) very beautiful.
They are (,if not perfect,) very beautiful.