Question 6) 5 points. Multiple-choice question: Choose one answer only. Which of the following is true of stacks and queues? a) A stack is a last-in, first-out structure, and a queue is a first-in, first-out structure. b) A stack is a first-in, first-out structure, and both structures are random access structures. c) A stack is a last-in, first-out structure, and a queue is a random access structure. d) A queue is a last-in, first-out structure, and a stack is a first-in, first-out structure. Question 7) 10 points. Multiple-choice question: Choose one answer only. How many times the operation inside the while loop will be executed? n is a positive number and indicates the input size. int j = n; while (j > 0) j = j/4; a) O(n/4) b) O(n) c) O(log n) d) O(n log n) e) O(1)