However, he went on to explain that he was not too sure about two things.

参考译文：然而，他继续解释他不太确信2件事情。

参考译文:然而，他继续又解释他对2件事情不太有把握。

请问，本句中介词短语about two things做句子的什么成分呢？是状语吗？是怎么状语呢？

谢谢！

回答如下：

about two things 是与依附在形容词上并与形容词一起构成形容词短语作“宾语从句的”表语成分

be sure about sth 结构 对某事很确定/很肯定/很有把握

be sure about sth /doing sth 确信某事/做某事；对某事/做某事有把握

It is impossible to be sure about the value of land.  

土地的价值是无法确定的。

You can be sure about their interest in it.  

你可以肯定他们对引很感兴趣.

To cross the river, one has to be sure about stones at the bottom.  

摸着石头过河.

I feel quite sure about getting the scholarship.
我很确信能得到奖学金。

（备注：以上结构为："be +形容词+介词"结构)

(1) be happy about

(2)be angry with

(3) be angry at 

(4) be kind to 

(5) be harmful to 

(6) be bad for

(7) be good for