i'm moving to the countryside because the air there is much fresher than { }in the city.a.ones b.one c.that d.those为什么选择ccars do cause us some health problems ---in fact far more serious{ }that mobile phones do.a.one b.ones c.it d.those为

Question

i'm moving to the countryside because the air there is much fresher than { }in the city.
a.ones b.one c.that d.those为什么选择c
cars do cause us some health problems ---in fact far more serious{ }that mobile phones do.
a.one b.ones c.it d.those
为什么选择b 综合分析俩题谢谢

Answer 1

上文已提及的事物 如the air 和problems 下文再提及时用one（复数ones）或that（复数those）.若用one则表示这个提及到的事物的同类,但并非提及的那一个,如：Your new pen is nice,I want to buy one.表示要买的是另一支笔；若用that表示则是专指上文提到的那一个,如：Your new pen is nice,I want to buy that.表示要买的就是你手上的那一支笔.
第一题空中特指上文提到的country air,第二题空中的problem应是指phone cause的,所以是同类事物