Judging from the Brief Descriptions Below, Which One of These

Judging from the brief descriptions below, which one of these four teachers is using a mastery learning approach?

A) Mr.Andrews lectures each week on different Canadian novels.Students must attend at least 80% of these lectures.
B) Ms.Bennett begins each class by asking students what they would most like to study that day.
C) Mr.Gagne has divided his physics course into 15 discrete units that students study individually at their own rate.
D) Ms.Bergeron teaches children the basics of mathematics by using such concrete objects as blocks and sticks.