A Teacher Wants to Encourage Her Students to Work Cooperatively

A teacher wants to encourage her students to work cooperatively with one another as they study classroom subject matter. Which one of the following strategies reflects the principle that some antecedent stimuli tend to elicit certain kinds of responses?

A) Praise students after they cooperate with one another.
B) Use mild punishment with students who are not working cooperatively with one another.
C) Say "I like how Sally and John are helping one another today" loudly enough that other students can hear.
D) Provide instructional materials that students can use only by working together.