122. And scores of online discussion boards have popped up on which people discuss negative experiences tied to too much time on the Web.
译文
网上突然出现了很多讨论区，专门讨论花太多时间上网的负面体验。
点睛
本句的主干是boards have popped up。on which引导的是以online discussion boards为先行词的定语从句，起补充说明作用，其中过去分词短语tied to too much time on the Web作negative experiences的后置定语，tied与negative experiences为被动关系。
pop up的意思是“突然出现，冒出来”。如：
After the rain, mushrooms seem to pop up overnight. 下过雨后，蘑菇似乎一夜之间就冒了出来。
tie...to...的意思是“使紧密结合”。如：
Our success is tied to you. 我们是否成功和你紧密相关。
考点归纳
过去分词短语作定语时，通常放在所修饰的词之后，实际上相当于一个定语从句。如：
These are problems left over by history.＝These are problems that/which are left over by history. 这些是历史遗留下来的问题。
I like the idea presented by my dad.＝I like the idea that/which is presented by my dad. 我喜欢爸爸提出的主意。
She is the first nurse trained by their country.＝She is the first nurse that/who is trained by their country. 她是她们国家自己培养的首位护士。
