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
网友回答
(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。