We must have the goods not later than 20th October _____ our sto

We must have the goods not later than 20th October _____ our stock is running short.
A、when
B、that
C、which
D、as
【正确答案】：D
【题目解析】：句意：我们的库存快要用完了，所以货不能迟于10月20日收到。as在这里意为”因为“；when意为”当......时“，不符语境；选项B和C也不符合语境。