Question

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

A．discovered	B．have discovered
C．had been discovered	D．have been discovered

Answer 1

D

时态和语态。由句中的时间状语in the past years可知，空格应填现在完成时；又因句子中的主语new substances与discover为被动关系，故选D项。