Question

CCTV is exactly like a window on the world ________ you will sit by it and fix your attention on what it shows.

1. A.
   if
2. B.
   as
3. C.
   while
4. D.
   unless

Answer 1

A
if引导状语从句表示一个假设。 假如你坐下来看节目，就会了解这一点。