As is known, it was Hu Jintao, _______ president of our nation, who gave ________ lecture at the ceremony of National Day

A．the; a

B．the ; /

C．a; the

D．/; a

医用显示器的分辨力包括空间分辨力和密度分辨力。密度分辨力用什么来度量（）.

A.离散像素数

B.可寻址像素数

C.可寻址灰阶数

D.离散灰阶级的总数

E.离散光通量