Which statement correctly compares the number of patients seen by the doctor on monday and tuesday?
a. on tuesday, the doctor saw 4 more patients per hour.
b. on monday, the doctor saw 4 more patients per hour.
c. on monday, the doctor saw 1 more patient per hour.
d. on tuesday, the doctor saw 1 more patient per hour.

Statements reasons 1. ab ≅ cd; ad ≅ bc 1. given 2. ac ≅ ac 2. reflexive property 3. △adc ≅ △cba 3. ? 4. ∠dac ≅ ∠bca; ∠acd ≅ ∠cab 4. cpctc 5. ∠dac and ∠bca are alt. int. ∠s; ∠acd and ∠cab are alt. int. ∠s 5. definition of alternate interior angles 6. ab ∥ cd; ad ∥ bc 6. converse of the alternate interior angles theorem 7. abcd is a parallelogram 7. definition of parallelogram what is the missing reason in step 3?