If you haven’t got the service advertised on their website, then you have to plain about it.
A. choice
B. purpose
C. right
D. reason
网友回答
A. choice
B. purpose
C. right
(答案→)D. reason
解析：reason理由，原因。have reason to do sth有理由做某事。句意：如果你没有得到网站广告中的服务，那么你就有理由投诉它。选D项。choice选择；purpose目的；right权利。