he explain the reason for his being late……for his being late

his being late是宾语,是介词for所带的宾语.
for his being late整体是介词短语,做后置定语,修饰the reason.
整个句子结构是这样的：
主语he+谓语explain+宾语the reason+定语for his being late.
后置定语和补语的区别：
后置定语是修饰前面的名词的,定语和中心词翻译成汉语往往可以在中间在一个“的”,如：
the reason for his being late他迟到的原因
the man in red穿红衣服的人
补语是补充说明前面的名词的.补语与宾语有逻辑上的主谓关系,换句话说,宾语与补语看起来像一句话.如：
I saw Jim reading a book.我看见吉姆在读书.
其中的reading a book就是补语,它与宾语看起来像一句话：吉姆在读书.
再问： 还有人说for his being late做状语，修饰前面整个一句话，对吗，为啥不对，怎么解释，怎么理解状语？
再答： 状语是修饰动词的。如：
I bought a present for you. 这里的for you是修饰bought的。
如果修饰一句话，那也要与主句用逗号隔开。这种情况很少见。
再问： I bought a present for you,这为啥不是for you做定语啊，后置定语修饰present ,给你的礼物。蒙了又
再答： 是为你“买”的。