Three of the Teachers Below Are Using Strategies Consistent with the Textbook's

Three of the teachers below are using strategies consistent with the textbook's recommendations for holding class discussions. Which teacher is using a strategy that is not consistent with the textbook's recommendations?

A) Mr. Poston assures students that it's okay if they change their minds about an issue.
B) Mr. Morris has students discuss a topic about which they know almost nothing.
C) Mr. Sheehan reminds students that they can criticize ideas but not people.
D) Mr. Retzlaff divides his class into groups of four students each to discuss a controversial issue.