An algorithm is shown below. Which of the following statements more correctly explains on how this algorithm is designed and implemented? Sum 1(A,1,1) if (=r return A[l] else { temp1 = Sum 1(AL (1 + r)/2) temp2 = Sum1(A, (1 + r)/2 + 1, r]) return (temp1 + temp2) } Select one: O a. designed and implemented using divide-and-conquer problem solving strategy b. designed and implemented using reduce-and-conquer problem solving strategy O c. designed using reduce-and-conquer problem solving strategy and implemented using recursive structure O d. designed using divide-and-conquer problem solving strategy and implemented using recursive structure