本句应该用declined，表示对别人的好意的礼貌拒绝

To refuse usually implies determination and often brusqueness  通常暗示决心且常带有粗鲁

If you refuse to do something, you deliberately do not do it, or you say firmly that you will not do it. 拒绝

“The commander refused to discuss questions of right” (George Bancroft). 

“司令官拒绝讨论关于权力的问题” （乔治·班克罗夫特）。

He refused to comment after the trial.  该审判之后他拒绝发表评论。

To decline is to refuse courteously 礼貌地拒绝

If you decline something or decline to do something, you politely refuse to accept it or do it. 谢绝

He declined their invitation. 他谢绝了他们的邀请。

He offered the boys some coffee. They declined politely.

 他要给男孩们来些咖啡。他们礼貌地拒绝了。

附带说一个reject

Reject suggests the discarding of someone or something as unsatisfactory, defective, or useless; it implies categorical refusal. 表示因为不令人满意、有缺陷或无用而抛弃；它暗示无条件的拒绝。

“He again offered himself for enlistment and was again rejected” (Arthur S.M. Hutchinson). 

“他再次要求应征入伍，结果再次被回绝了” （亚瑟·S.M.霍金森）。

三个里reject 拒绝的强度最大，decline 最小。