Genevieve wants her students to learn how to read their textbooks to answer questions about the material. she has her students do an ungraded in-class activity where they read sections of the book and answer questions about what they read on an activity sheet. a few weeks later, genevieve assigns an activity sheet to go with her students’ reading, but this time they receive a grade for finding the answers in the text. if the students do a good job and earn high grades on their answers, then their performance is most likely a result of: