题目

_______ Jenny was reading a book yesterday, someone knocked at the door. A) Since            B) While           C) Although   D) If 答案： B函数y=x2+2x（x＜-1）的反函数是A.（x＜-1）B.（x＞-1）C.（x＜-1）D.（x＞-1）