It’s suggested that everyone should at least one hour a day to keep fit.
A. work for
B. work out
C. work at
D. work on
网友回答
A. work for
(答案→)B. work out
C. work at
D. work on
解析：考查短语辨析。work for 为了什么工作， work out 算出，锻炼身体，work at 在上班，work on 从事，句意：据建议每个人应该一天至少锻炼一小时来保持健康。所以选B。