This question has options. Answer the question about text:

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 .

Why did the sky appear clearer ?
OPTIONS:
I. None of the above choices ..
II. The citizens learned to ignore the gloomy skies ..
III. The citizens made an effort to cut down on pollution ..
IV. A large storm had recently passed ..
III.