Read the passage by Peter N. Sterns. The past causes the present, and so the future. Any time we try to know why something happened . . . we have to look for factors that took shape earlier.
I WILL MARK BRAINLEST IF CORRECT HELP PLS
According to the writer, why is it important to study history?

so we can see how things change over time
so we can understand how the present came to be
so we can learn interesting facts about the past
so we do not repeat mistakes of the past

Given: ab ≅ cd and ad ≅ bc prove: abcd is a parallelogram. 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? triangle angle sum theorem sas congruency theorem sss congruency theorem cpctc