Which set of ordered pairs is a function? {(-21).(-4, 2), (0, 3), (4,1),(-2,5)}
{(-1,5), (-1,4),(-1,3), (-1,2), (-1,1)}
{(-6, -4), (-4,-2), (0,0).(-4, 2). (-6,4)}
{(-5,1). (-3, 2), (-1,3), (1,4), (3,5)}

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?