单选题 Annie Jump Cannon,______discovered so many stars that she was called "the census taker of the sky".
A. a leading astronomer, B. who, as a leading astronomer,
C. was a leading astronomer, D. a leading astronomer who

【正确答案】 A

【答案解析】[解析] 结构识别。
a leading astronomer是Annie Jump Cannon的同位语。