Facing the great selections of these courses这是现在分词短语 作状语 相当于一个状语从句 因为与句子主语是主动关系故 用现在分词
some people是主语 say是谓语
that,history classes should be made compulsory for college students是宾语 .
原句= when some people face the great selections of these courses,they say that history classes should be made compulsory for college students
当从句 中的主语 与主句主语 一致 时 可以用分词短语 代替 状语从句