Read the following context and choose the best option to answer the question.
Context: Two things happened today in Beijing . First off , incoming journalists were amazed to find China had successfully lifted the brown haze in city . Skies were crystal blue and the air felt noticeably lighter .
Question: Why did the sky appear clearer ?
Options: 
A. None of the above choices .
B. The citizens learned to ignore the gloomy skies .
C. The citizens made an effort to cut down on pollution .
D. A large storm had recently passed .


C