Triangle ABC is a right triangle. Point D is the midpoint of side AB, and point E is the midpoint of side AC. The measure of ∠ADE is 68°. Triangle ABC with segment DE. Angle ADE measures 68 degrees. The proof, with a missing reason, proves that the measure of ∠ECB is 22°. Statement Reason m∠ADE = 68° Given m∠DAE = 90° Definition of a right angle m∠AED = 22° Triangle Sum Theorem segment DE joins the midpoints of segment AB and segment AC Given segment DE is parallel to segment BC ? ∠ECB ≅ ∠AED Corresponding angles are congruent m∠ECB = 22° Substitution property Which of the following can be used to fill in the missing reason? A. Triangle Inequality Theorem B. Midsegment of a Triangle Theorem C. Concurrency of Medians Theorem D. Isosceles Triangle Theorem