题目

设函数f(x)=,则 (a≠b)的值应为(    ) A.|a|                                    B.|b|C.a、b之中较小的数               D.a、b之中较大的数 答案：答案：D解析:①当a＞b时,a-b＞0,f(a-b)=1,原式==a;②当a＜b时,a-b＜0,f(a-b)=-1,原式==b.综合①②可知,原式=Along with his letter was his promise ________ he would visit me this coming week． [　　] A．whichB．thatC．whatD．whether