The missing boys were last seen ____

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The missing boys were last seen ________ near the river.

  • A. playing
  • B.played
  • C.play
  • D.to play

参考答案:

A

所填的词为主语补足语,因其后有明确的地点,补足语表示动作当时正在进行中,所以只能使用 playing 。