— Have you heard that a building was blown up last weekend with a number of people in it?

— Yes, _____ news came as _____ shock to me. [ ]

A. / ; the

B. the; a

C. a ; a

D. the; the

为了避免色信号对亮度信号产生干扰，在NTSC制中色副载波选择为半行频的（）倍，PAL制中则按1/4行频间置选择副载波。