【题目】After a heated discussion, they still don’t know at all _______.
A. what is he working outB. what he is working on
C. what did he work onD. what he is working out
在线课程【答案】B
【解析】
考查动词短语和宾语从句。句意：经过激烈的讨论，他们仍然一点也不知道他在做什么。work on表示“从事于”，work out表示“算出”，分析句子结构可知此处为宾语从句，从句中的working on缺少宾语，故B项正确。