问题描述：
It is said that the early European playing-cards ______ for entertainment and education.
A.were being designed B.have designed
C.have been designed D.were designed
但是design发生在it is said 之前为什么不用完成时呢?
A.were being designed B.have designed
C.have been designed D.were designed
但是design发生在it is said 之前为什么不用完成时呢?
问题解答：
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