A vast area north of the Yangtze River by the first heavy snow of the new year,causing difficulties to the post-festival road transport.
A. were affected
B. was affected
C. had affected
D. has affected
网友回答
A. were affected
(答案→)B. was affected
C. had affected
D. has affected
解析：句子的主语为A vast area north of the Yangtze River，所以谓语动词要用单数形式，只能在B项和D项中选择；又因为D项语态不对，所以正确答案为B项。