(1 point) Let r be a relation on the set A = {1, 2, . . . , 20}. Which of the following statements are true? Select all that apply. [:1 A. If (0, 10), 10,5), (5, 15 are all elements of r, and r is transitive, then (0, 15) must be an element of 1'. [3 B. If (0, 15), 15,5), (5, 10 are all elements of r, then (0, 10) must be an element of PL (the transitive closure of r). (5 1 (5 1 ( ) ( ) C] C. If (0, 10), (10, 5), , 5) are all elements of r, then (0, 15) must be an element of 11-3. C] D. |f(0, 15), (15,5), , 0) are all elements of r, then (0, 10) must be an element of 1'. Hint: Make sure you understand problem 1! Also, if r is transitive, then 1- : r+. (Why?)