Answer:
It is the square (I'm assuming that one is D)
Step-by-step explanation:
Note that it specifically states that it is a "square pyramid". This means that the base is a square, and the other 4 sides create the pyramid.
Also note that the cross-section cuts by a plane "parallel to the base", suggesting that it will have the same shape as the base.
Since the base is a square, ∴ the plane cross-section will also be a square.
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