2002 Gauss 8 Problem 10

Which of the following statements is not true?

\textbf{(A)} A quadrilateral has four sides. \textbf{(B)}\ The sum of the angles in a triangle is 180^\circ.\quad \textbf{(C)}\ A rectangle has four 90^\circ angles.\quad \textbf{(D)}\ A triangle can have two 90^\circ angles.\quad \textbf{(E)} A rectangle is a quadrilateral.

If there are no answer choices shown, enter a numerical answer.

Full credit to this problem is given to the CEMC, you may view all Gauss contests here.