Which jigsaw pieces fit to make a create a square?

What is the quickest way to solve such a question below? I have tried different rotations to fit them as a square, but couldn't make it work.

Four of the five jigsaw pieces shown below fit together to make a square. Which one of these diagrams does not fit?

Solution 1:

Observe that the least number of little squares in the final figure would be $4+5+6+7=22$ and the most number of little squares equals $5+6+7+8=26$. Since the final figure is a square, it obviously has $25$ little squares. This means the second figure isn't used.

Solution 2:

As all others have pointed out, you can just count the number of boxes to figure out that the square will have to be a 5x5 square and that B is the piece that will not be used. But if you are still interested in how that square is made:

Put D to the left of C to form the base of the square. Rotate E 180 degrees and put on top of this. The A piece will now fit the remaining space.