What happened to him? I don’t know_________________（宾语从句）

What happened to him? I don’t know_________________（宾语从句） I don't know what to see.(改为宾语从句） I don't know ______ ______ I don't know what to do (改为含有宾语从句的复合句） i don't kown what to say .(改为宾语从句） 关于宾语从句I don't know------with him yesterday .为什么选择what was th I don't know what to do中what to do是宾语从句吗? I don't know what to do next 改成宾语从句 I don't know what to do next.改为宾语从句 I don't know what happened to her. 请问 I don't know what happened 是宾语从句吗?关系代词 后面没有主语直接谓语也可以吗?比如像 What should I do.引导宾语从句.还有就是例：I don’t know what to do 请问I don't know what to do next.中的what to do next是宾语从句吗?为什么?