请问这道英语选择题的结构是什么?With his son ( ),the old man felt unhappy.

请问这道英语选择题的结构是什么?With his son ( ),the old man felt unhappy.
A.to disappoint B.to be disappointed
C.disappointing D.being disappointed
正确答案选择C项.请问这道题的句子是什么结构?为什么选择C?整句怎么翻译?