问题
选择题
Because of the Mid-autumn Day happening to come along, we have just enjoyed a longer National Day vacation than ever before, but it is estimated that it will be 38 years ___________ we can experience such a coincidence again.
A．that
B．before
C．since
D．when
答案
：B
：考查特殊句式。句式：It be+一段时间 before从句。表示：一段时间以后某事才发生。句意：据估计38年以后我们才能又一次经历这样的巧合。故B正确。本句式的考查务必要注意时态，before从句里用一般现在时代替将来时，前面的主句用将来时。