Please do your most to establish the covering L/C _______ we can

Please do your most to establish the covering L/C _______ we can arrange the shipmentsmoothly.
A、as
B、so as to
C、so that
D、such that
【正确答案】：C
【题目解析】：so that以至于句意：请尽最大努力开立有关信用证，以便我们能顺利地安排装运。