题目

 Without the help of the PLA men, all 69 miners trapped in a flooded coal mine in Henan Province for three days ________ . A. couldn't rescue                                            B. couldn't have been rescued C. shouldn't have rescued                                   D. hadn't been rescued 答案：B叶绿体和线粒体的功能是（　　）A．保护细胞B．储存遗传物质C．进行物质交换D．进行能量转换