that when you exercise,your body produces
some chemicals that make you feel peaceful and relaxed and increase your ability to
concentrate when you study
1.它是主系表结构.
2.具体分析如下：
主语：Many teenagers
系动词：are
表语：surprised
(原因)状语：to learn that when you exercise,your body produces
some chemicals that make you feel peaceful and relaxed and increase your ability to concentrate when you study.
注：此句用不定式做原因状语,再如：
I'm sorry to hear the news.
3.做原因状语的不定式中的learn后面是一个以that作为引导词的宾语从句.
该宾语从句结构分析如下：
when you exercise为宾语从句中的时间状语从句（其中的you和exercise分别为时间状语从句的主语和谓语）；
your body为主语；
produces为谓语；
some chemicals为宾语；
其后的that make you feel peaceful and relaxed and increase your ability to concentrate when you study为定语从句,修饰chemcals做定语.
4.该定语从句分析如下：
1）that即是定语从句的关系代词/引导词,又在定语从句中充当主语,相当于先行词chemicals；
2）make为谓语；
3）you为宾语；
4）feel peaceful and relaxed以及increase your ability to concentrate为用and并列的两个宾语补足语；
其中to concentrate为不定式做后置定语,修饰ability；
5）when you study为时间状语从句,其中you和study为主语/谓语.