What are they doing? [ ]

A. She is singing.

B. He is crying.

C. They are talking.

关于血细胞计数的描述，正确的是

A．采血应挤压皮肤
B．固有误差即计数域误差
C．多次计数取平均值可消灭固有误差
D．采血部位不当不属于技术误差
E．产生气泡不会影响计数结果