题目

Nobody believed his reason for being absent from the class _____ he had to meet his uncle at the airport.   A. why       B. that C. where       D. because 答案：B  题干中的reason是同位语从句中的先行名词，该名词和其后的从句被介词短语分隔，这样给解题造成一定的难度。reason后的同位语从句用that引导。  不改变分式的值，使分式的分子分母各项系数都化为整数，结果是（        ）。