When asked to explain _____ he did to make his students so fascinated with his lessons, the teacher paused and thought deeply.

A．what was it that

B．that what it was

C．what it was that

D．what was it

嗜酸性粒细胞乙醇伊红稀释液中加入碳酸钾的作用是（）。

A．破坏白细胞、红细胞

B．保护嗜酸性粒细胞

C．使嗜酸性粒细胞着色

D．为嗜酸性粒细胞保护剂

E．减少乙醇挥发