We thank you very much for your L/C and shipping instructions __

We thank you very much for your L/C and shipping instructions _______ your trial order.
A、being covered
B、to be covered
C、covering
D、covers
【正确答案】：C
【题目解析】：cover在句子中做非谓语，非谓语有三种形式：to do、doing和done。