Bluebird wrote:

What is the are of parallelogram ABCD?

[1] AB = BC = CD = DA = 1

[2] AC = BD = sqrt(2)

I think the answer is B, because we know the diagonal of a square is s*sqrt(2), where s = the length of a side of the square, and if we know the two diagonals of this parallelogram are equal then we know it is a square, right? Can we not assume that the side is 1 given that we know the diagonal?

The OA is: C

C is correct.

It can be rhombus from stmnt 2. Only by combining stmnt 1 , we can prove its a sqaure.