They have no idea at all .A. what he is working onB. what is he working onC. what did he w

问题补充：

They have no idea at all .

A. what he is working on

B. what is he working on

C. what did he work on

D. what he is working

答案：

(答案→)A. what he is working on

B. what is he working on

C. what did he work on

D. what he is working

解析：名词性从句.定语从句中应用陈述语序结构，故选A。