Which early intervention found positive results that lasted until program participants were 21 years old?

Five-month-old Patricia has learned to clap her hands and play patty-cake when her sister claps her hands and smiles. In which of the following behaviors is Patricia engaging?

acquired adaptation making interesting sights last active experimentation making mental combinations

Professor Todd decides to test her hypothesis that eating chocolate prior to exams increases students' test scores

She randomly assigns students to two groups at the beginning of the semester. One group receives a bar of chocolate before each test, while the other group receives another type of candy. She compares their scores at the end of the year, and finds that the students who ate the chocolate scored an average of ten points higher on their exams. What is the dependent variable in this experiment? A) Students' test scores B) Chocolate bars C) The students themselves D) The professor