问题补充：
When something is on fire, people throw sand on it to put out the fire. The main use of the sand is to .
A. protect the thing on fire
B. add weigh to the thing on fire
C. keep the air away from the thing on fire
D. lower the temperature of the thing on fire
答案：
A. protect the thing on fire
B. add weigh to the thing on fire
(答案→)C. keep the air away from the thing on fire
D. lower the temperature of the thing on fire
解析：句意：当某物起火的时候，人们扔沙子在火上面。主要目的是用沙子去阻止空气与火的接触。考查固定短语：keep sth. away from sth.保持某物远离某物。故选C
