题目内容
---What is the boy doing?
---He _____________ happily.
A swims B swam C has swum D is swimming
---He _____________ happily.
A swims B swam C has swum D is swimming
D
问句是：What is the boy doing?说明是用现在进行时，选D。
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问句是：What is the boy doing?说明是用现在进行时，选D。