When and why he came here () yet?A is not known B are not known C has not known D have not been

When and why he came here () yet?A is not known B are not known C has not known D have not been
When and why he came here () yet?A is not known B are not known C has not known D have not been

When and why he came here () yet?A is not known B are not known C has not known D have not been
你好,应该是：
A
翻译为 他何时为什么来这儿还不清楚.
句子的主语是whne and why he came here,是一件事
所以为单数
如果用have,应该用被动
所以只能选A
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A
他何时及为何来这里还不知道呢。
首先应用被动语态，先排除C；其次“他何时及为何来的事实”用单数，再排除B和D
希望对你有帮助

选择A,
这题是把when and why he came here 他何时，为什么来这的原因当作一件事情来看，当作一个整体，所以用is