Why Would a Science Teacher Insist That the Students Keep

Why would a science teacher insist that the students keep portfolios even though it takes quite a bit of the teacher's time to keep up with them?

A) To enable the teacher to assess what the students really know and what they have learned
B) To provide authentic assessment
C) To enable the students to keep track of their progress in science
D) To provide meaningful sets of documents to share with parents
E) All of the above
F) None of the above