Jack and Ketty _______ in the lake. Let's join them, shall we?

  • A swim
  • B have swum
  • C swam
  • D are swimming
参考答案: D
解题思路: 句意:Jack和Ketty正在湖里游泳。让我们加入他们吧,好吗?根据句意,应用现在进行时:be+动词ing形式。故选D.