题目内容：

the delay is ___ our having difficulties in obtaining materials.
A due to B because of
请问不能用B的原因是

优质解答

本题选A
due to 和 because of都可以表明“因为”,但
due to 往往用来解释一个事件（尤其是不好的事情）的起因,可翻译成“归罪于”
because of 没有这层意思.
单选不只是选择对的,更是选优,哪个更合适就选哪个.没选的未必就是错的.