题目内容：

___ they have been working hard to find?Ais that what Bis that Cit is that Dis it that

优质解答

选A,这里that是指示代词,“那个,那”
把这句话变为陈述语序你就懂了
That is what they have been working hard to find
那就是他们努力工作去寻找的东西