505.Sometimes proper answers are not far to seek _____ food safety problem.
A.in
B.to
C.on
D.after
506.I always wanted to do the job which I'd been trained _____.
A.on
B.for
C.by
D.of
505.答案是B;考查介词的用法。
506.答案是B;此题以定语从句的形式考查介词的用法。其中train sb.for the job意为:为这项工作而培训某人。
