题目

具有“胎生和哺乳”特征的动物是 A．蚯蚓              B．草鱼                  C．啄木鸟              D．大熊猫 答案：DThis river ________ very clean. Now it’s getting dirtier and dirtier. 　　 A. used be B. used to be C. used being D. is used to be