问题补充:
The machine has been used many years. It’s no wonder that it doesn’t work well.
A. regularly
B. constantly
C. occasionally
D. frequently
答案:
A. regularly
B. constantly
(答案→)C. occasionally
D. frequently
解析:A. regularly定期地,B. constantly 连续地,不断地,C. occasionally偶尔地,D. frequently经常地,句意:这个机器已经被使用了很多年,难怪它偶尔不工作了。所以选C。