句1主语省略（可能是people,we之类的单词）,谓语know,宾语British people ,being formal是宾补.
句2主语the school,谓语did,宾语this,状语是reduce the trouble,caused by student fashion是trouble的定语.
句3主语students 谓语are（系动词）at school是表语, to study目的状语 .
找找主谓宾定状补1.British people are known being very formal .2.The