现在分词作状语和句子的主语之间是主动关系,过去分词作状语和句子的主语之间是被动关系．比如
Followed by the students,the teacher walked into the classroom.在这个句子中,老师是主语,过去分词短语做伴随状语,the teacher 和follow 之间是被动的关系．是老师被跟．
Following the teacher, the students came to a library.在这个句子中,学生是主语,是学生跟着老师,所以用了现在分词．