With more and more farmers moving to cities, an inadequate labor force is being a major factor affecting the country's grain output.
A. automatically
B. occasionally
C. absolutely
D. gradually
网友回答
A. automatically
B. occasionally
C. absolutely
(答案→)D. gradually
解析：考查副词辨析。A自动地；B偶然地；C绝对地；完全地；D逐渐地；句意：随着越来越多的农民进城，劳动力不足逐渐成为影响这个国家粮食产量的一个主要因素。根据句意说明D正确。