Pointing to a boy in photograph, Reena said, 'He is the only son of the only child of my grandfather.'
How is Reena related?
I. Mother
II. Sister
III. Aunt
IV. Cannot be determined

Question: 以下哪项是正确的？
Options:
A. 仅 I, B. 仅 IV, C. 仅 III, D. II 为真
Answer: D
True statement: II