问题
选择题
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
答案
答案：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。