______ your sister at home yesterday? No, she watched a film with my mother.A. Was B. Were C. Did
下列食物链正确的是:()
根部吸收的水分可以向上输送到植物的顶,主要动力来自()
导管的功能是()
属于生态系统的是()
下列有关人体构成正确的是()