— How did you do in your essay?

— I got ____ okay grade, but Mr. Jones gave Sarah top marks. She's ____ teacher's pet, you know.[ ]

A. 不填; a

B. an; 不填

C. 不填; the

D. an; a

委托事故发生单位调查的一般事故，事故调查报告应当报经事故发生地电力公司同意。