-I apologize for not being able to join you for dinner.-----

I apoliogize for (not) doing sth。我为没能做。。。像。。。道歉。相当于：I'm sorry that 。。。/ for 。。。只是apologize 更书面化。一般对于道歉的回答“不要紧；不必顾虑”有：it's OK。that's/it's all right。not to worry。forget it。It doesn't matter。never mind。排除B、C。Go ahead,继续。。。这样看来没符合的。别急,其实 don't mention it不谢；不用谢；无足挂齿；没关系。我们常说抱歉时,都可以用D回答的。所以正确答案是D。这是常考题。