Ateamofscientists的精選

問題詳情：Ateamofscientists_____theeffectsofacidrainoverthelasttwenty﹣yearperiod．（）A．studied B．hadstudiedC．isstudying  D．hasbeenstudying【回答】D知識點：動詞時態與語態題型：選擇題...