加入5%柠檬酸钠的血液静置一会儿后,中间一层白色物质是( )
A:白细胞和红细胞
B:血小板
C:红细胞和血小板
D:白细胞和血小板
下列盆地中,位于青藏地区的是( )
下图是周日在公园的活动。请按图示内容完成短文。
I'm Kate. It's Sunday today. I don't go to school. I go to the park with my parents. There are many people here. Look! ____ .____ .____ .____ .____ .We are very happy.