Final answer:
To find the next numbers in the sequence, subtract 9 from each number and then add 5 to the result.
Step-by-step explanation:
The sequence is: 21 - 71 - 38 - 51 - 32. To determine the next numbers in the sequence, let's analyze the pattern. Subtracting each number by 9, we get: 12 - 62 - 29 - 42 - 23. This gives us a new sequence. Adding 5 to each number in the new sequence, we get: 17 - 67 - 34 - 47 - 28. Therefore, the best numbers to come next in the original sequence are 17-67-34-47-28 (d).