单项选择__ 74 cities in China adopted the new strict air quality standards in 2013,only three out of 74 cities's air quality
问题描述：
单项选择__ 74 cities in China adopted the new strict air quality standards in 2013,only three out of 74 cities's air quality is up to standard.
A.Since B.Although
答
答案为B.
考查连词的使用.since“自从；既然”,although“尽管,虽然”.
根据句意：
在2013年,虽然中国有74个城市采用了新的严格的空气质量标准,但是其中只有三个城市空气质量达到标准.
可知答案为B.