We have been happy to _________ your credit based on your promis

We have been happy to _________ your credit based on your promise to pay according to our terms.
A、expand
B、prolong
C、extend
D、lengthen
【正确答案】：C
【题目解析】：expand扩大；prolong延长，拖延；extend延伸，伸展；lengthen延长，加长句意：我们很乐意在你方承诺按照我们的条件付款的基础上，扩大你方的信用。