题目

The Beijing Hearing Dog Association has a plan.They plan to choose some stray dogs (流浪狗) and train them.Then the dogs will be able to help the old and the deaf.They will choose young dogs，because it's easier to train them.The kind of dog is not important.Twenty－four volunteers will join the training.They all have some experience of keeping dogs and they all love dogs.They will learn a special language first from the coach(教练) and they teach the dogs.This training will take 180 days.Then the better－performed dogs will enter the next training.They will learn to understand differe分析以下四种细胞器，错误的说法是（ ）A．丁存在于动物细胞和某些低等植物细胞中B．乙是由单层膜围成的网状结构，是脂质合成的车间C．丙内含有多种物质，可以调节植物细胞内的环境D．上述四种细胞器的膜参与构成细胞的生物膜系统