The boy pretended       when his parents entered the room.

A．reading

B．to reading

C．to be reading

D．having read

红细胞直方图显示曲线主峰左移，峰底正常，常见于()

A．缺铁性贫血

B．小细胞均一性贫血

C．铁粒幼细胞性贫血

D．再生障碍性贫血

E．巨幼细胞性贫血