◎ 题干
There are a lot of useful things on the Internet,  but________,there is something unhealthy on it. 
[     ]
A. by the time    
B. at the same time    
C. all the time
◎ 答案
查看答案
◎ 解析
查看解析
◎ 知识点
    根据n多题专家分析,试题“There are a lot of useful things on the Internet,but________,there is something unhealthy on it.[ ]A. by the timeB. at the same timeC. all the time…”主要考查了你对  【介词短语】  等知识点的理解和应用能力。关于这些知识点的“档案”,你可以点击相应的链接进行查看和学习。