In this diagram, CD is the perpendicular bisector of AB. The two-column proof shows that AC is congruent to BC. Which of the following would justify step 6?
Step 1 : CD is the perpendicular bisector of AB. Justification: Given
Step 2: AD =`` BD (AD is congruent to BD). Justification: Definition of bisector
Step 3: CD is congruent to CD. Justification: Reflexive Property of Congruence
Step 4: ADC and BDC are right angles. Justification: Definition of Perpendicular lines
Step 5: ADC is congruent to BDC. Justification: All right angles are congruent.
Step 6: ADC is congruent to BDC. Justification: ?
Step 7: AC is congruent to BC. Justification: CPCTC
Which of the following would justify step 6?
A) AAS
B) ASA
C) SAS
D) SSS