题目

The house was greatly damaged by the truck.We'd better leave things ________they are until the police arrive. A．since  B．as   C．though  D．unless 答案：B [句意：卡车对这座房子造成了严重损害，我们最好保持事物的原样等待警察到来。as引导方式状语从句，意为“按照……的方式”。leave things as they are意为“让一切顺其自然”。]如图，已知在△ABC中，BO平分∠ABC，CO平分∠ACB，且OM∥AB，ON∥AC，若CB=6，则△OMN的周长是（　　） A、3B、6C、9D、12