The writer ______ the question of environmental pollution in his

The writer ______ the question of environmental pollution in his article.
A、kept from
B、kept to
C、kept up
D、kept in
【正确答案】：C
【题目解析】：keep from阻止；keep to 坚守；keep up 不断，保持；keep in 隐藏；句意：作者在文章中不断提到环境污染问题。因此C符合题意。