The petrol tank is empty. I it up before we left home.A. had to fillB. would have filledC.

问题补充：

The petrol tank is empty. I it up before we left home.

A. had to fill

B. would have filled

C. should have filled

D. could have filled

答案：

A. had to fill

B. would have filled

(答案→)C. should have filled

D. could have filled

解析：根据本句中的before we left home可知这是对过去情况的虚拟。对过去情况的说明使用“情态动词+have done”，排除A项。Would have done本想做某事；should have done本应该做某事，实际上却未做；could have done本可以做某事，实际上却未做；句义：油箱空了，在离开家之前，我本应该把油箱加满的。故C正确。