题目

 If we had arrived here ten minutes earlier, we__________the bus.    A. would catch                                               B. would have caught      C. had caught                                               D. should caught 答案：B动物通过呼吸作用将体内的部分有机物分解成无机物，这体现动物在自然界中的作用（　　） A、促进生态系统的物质循环B、维持生态平衡C、帮助植物遗传D、帮助植物传播种子