【题目】The dog ________ attacked passers-by and therefore was kept on a chain by the owner.
A. eventually B. fortunately
C. frequently D. similarly
在线课程【答案】C
【解析】试题分析：A. eventually最后；B. fortunately幸运地；C. frequently经常地；D. similarly同样地。句意：这条狗经常地袭击过路者，因此被主人用链子绑住了。C项符合语境。