they have been working hard to find?A. Is that whatB. Is thatC. It is thatD. Is it that

问题补充：

they have been working hard to find?

A. Is that what

B. Is that

C. It is that

D. Is it that

答案：

(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。