Answer:
It cannot be concluded that ABCD is square.
Step-by-step explanation:
parallelogram is a quadrilateral whose opposite side are parallel
it may or may not have angles right angled.
For a quadrilateral to be square following condition should be satisfied
1: opposite side parallel
2: all side congruent
3: All angles right angle.
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coming back to question
given
Marcus shows that opposite sides are congruent and opposite sides are parallel.
He says that opposite sides are congruent but no information is given about adjacent side. Adjacent side should also be congruent
Also , criteria of right angle is not also mentioned which is mandatory to prove shape of square.
Based on above information,
ABCD can also be
Rectangle and Rhombus, as both also have opposite sides congruent and opposite sides parallel.
Hence, it cannot be concluded that ABCD is square.
