问题补充：
After a careful survey about the cause of the newly-built bridge, they finally came to a(n) that it was due to the heavy rain.
A. construction
B. motivation
C. conclusion
D. impression
答案：
A. construction
B. motivation
(答案→)C. conclusion
D. impression
解析：句意：在对新建的大桥的原因进行仔细的调查后，他们最后得出结论是由于大雨。四个选项的含义分别是：A. Construction建设，B. Motivation动机，激发，C. Conclusion结论，D. Impression印象，这里也使用了词组：come to conclusion得出结论，所以选C。
