【紧急】求助一个难句分析中THAT 到底起什么作用

clearskybird

The individual now has more informationavailable than any generation, and the task of
finding that one piece of information relevant to his or her specific problemis complicated,
time--consuming, and sometimes even overwhelming.   
请教各位大神，这个句子中 finding 后面的：that到底起什么作用呢？ 如果是引导宾语从句的话，那从句的谓语在哪呢。  非常感谢！！！！