请问they have been able to do的时态是什么?been able to 和 be able to的区别是什么?

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请问they have been able to do的时态是什么?been able to 和 be able to的区别是什么?
请问they have been able to do的时态是什么?been able to 和 be able to的区别是什么?

请问they have been able to do的时态是什么?been able to 和 be able to的区别是什么?
现在完成时 have been able to 是 be able to 的现在完成时