they have been working hard to find?
A. Is that what
B. Is that
C. It is that
D. Is it that
网友回答
(答案→)A. Is that what
B. Is that
C. It is that
D. Is it that
解析：首先确定本小题是问句，因此排除C选项；本小题That is后面的句子是表语从句，而后面的find缺乏宾语，因此要用what。B缺少find的宾语，D是强调句的一般疑问句形式。本小题“那就是他们一直苦苦寻找的。