亲,正确答案应该是：When,have.
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不过格式这句话有些矛盾哈,
应该是：When do you have a basketketball game?
或者：When do you play basketball?
因为如果单说have a basketball 或者 play a basketball
就代表有一个篮球或者玩一个篮球啦.
希望能帮助到您.