Before 1912,something like robots__(appear).怎么填,

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Before 1912,something like robots__(appear).怎么填,

Before 1912,something like robots__(appear).怎么填,
Before 1912,something like robots__(appear).怎么填,

Before 1912,something like robots__(appear).怎么填,
had been apeared 过去完成时 191已经是过去 而它在1912前出现 是过去的过去

appeared.
1912年以前,所以要用过去式。