is known to us all our government has spared no efforts to control food prices.A. WhatB.

问题补充：

is known to us all, our government has spared no efforts to control food prices.

A. What

B. Which

C. As

D. It

答案：

A. What

B. Which

(答案→)C. As

D. It

解析：C 考察非限制性定语从句。As放在句首，指代后面的整个句子，which通常放在主语后，what不引导定语从句，选what可以把句子改为What is is known to us all is that our government has spared no efforts to control food prices.故C正确。