题目

--- Could you tell me what time the train leaves Hefei for Beijing?     ---I'm afraid you need to _____ in the guidebook.     A. look for it      B. look at it   C. look it over     D. look it up 答案：D过点M（-3，2）作圆O：x2+y2+4x-2y+4=0的切线方程是    ．