With the help of high technology,more and more new substances[ ]in the past years.

题目

With the help of high technology,more and more new substances[ ]in the past years.
空中应填have been discovered而不是 had been discovered,为什么

答案

和现在有关的用have
和现在无关的用had
过去发现的物质对现在有影响,所以用have