问题补充：
The scientist’s many years’ careful observation a surprising discovery.
A. ran into
B. began with
C. led to
D. came from
答案：
A. ran into
B. began with
(答案→)C. led to
D. came from
解析： 考查短语辨析。ran into 偶然遇见，began with 以什么开始，led to 导致，came from 来自，句意：科学家们许多年的细心观察导致了一个令人吃惊的发现。所以选C。
