作业帮I don't know what was ___ on the playgroundA.happen B happened C chappens D happening
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I don't know what was ___ on the playgroundA.happen B happened C chappens D happening
I don't know what was ___ on the playground
A.happen B happened C chappens D happening
I don't know what was ___ on the playgroundA.happen B happened C chappens D happening
B happened
我不知道操场上(刚才)发生了什么事
要被动语态,因为是什么被发生了,如果D的话,你不能有 was.
be+V 过去分词为被动语态!
d(happen 不能用被动语态)
D happen无被动
选D，happen不用作被动语态，又前面有be动词was，所以用进行时态。
句意为：我不知道操场上发生了什么。