With the help of high technology, more and more substances _________ in the past years.
A．discoveredB．have discovered
C．had been discoveredD．have been discovered
D

試題分析：考查時態(tài)和語態(tài)。本題的關(guān)鍵是時間狀語in the past years，該時間狀語通常與現(xiàn)在完成時連用。既要：在高科技的幫助之下，在過去幾年里越來越多的物質(zhì)被發(fā)現(xiàn)了。根據(jù)驚句意說明使用被動語態(tài)的形式。故D正確。
點評：時態(tài)題的考查關(guān)鍵是抓住句子的上下文含義和句中的時間狀語。要根據(jù)時間狀語來選擇合適的時態(tài)，在平時的學(xué)習(xí)中要注意積累有關(guān)時態(tài)的用法和各種時態(tài)的特殊之處。如since， so far等經(jīng)常與現(xiàn)在完成時連用。在條件狀語從句中用一般現(xiàn)在時代替將來時等等。
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