With the help of high technology, more and more new substances _______ in the past years.
A.discoveredB.have discoveredC.had been discoveredD.have been discovered在线课程D
思路分析：由“in the past years”表一段时间知该题应用现在完成时，而substances与discover是被动关系，故选D。
点评：本题考查现在完成时的被动语态，难度中等。