题目

下列变形正确的是( )A. ＝ B. C. -1= D. = 答案：【答案】D【解析】根据分式的基本性质即可求出答案．解：(A)≠，故A错误；(B)＝，故B错误；(C)﹣1＝，故C错误；故选：D．It was not until she came to see us ____ her mother was ill in bed.A．when we knewB．that did we knewC．that we knewD．that did we know