Look at this series: 17, ____, 28, 39, 39
What number should fill the blank?
I. 50
II. 39
III. 25
IV. 17
Question: 以下哪项是正确的？
Options:
A. 以上各项均不成立, B. 只有 IV, C. IV 或 III, D. 仅 I, E. 仅 III
Answer: B, C