She programs us with all the possible moves she has seen while watching human games."she has seen "为什么要用现在完成时?

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She programs us with all the possible moves she has seen while watching human games.
"she has seen "为什么要用现在完成时?

过去完成时·see 是在program之前完成的动作或者说状态.

seen已经是过去式了,如果把has换成had,那这就成了已经过去式的句子了,可是这个句子是过去式。she是第3人称,所以后面要放has而不是。have只有4种形态,have,has,had和having。这个句子不是现在进行式,不可能放having。所以应该是has.