詞匯擴(kuò)充+語法訓(xùn)練exercise5
    More than 10,000 earthen mounds, built byA Bprehistoric Native Americans for ceremonial purposes,Cthey have found in Minnesota. No errorD E
    (A)
    (B)
    (C)
    (D)
    (E)
    Here's Why:
    The error in this sentence occurs at (D), where there is an unnecessary pronoun and an inappropriate verb form. There is nothing in the sentence to which “they” can logically refer. In addition, the sentence needs a main verb (“have been found”) for its subject (“earthen mounds”).