In Which of the Following Situations Would One Use an Independent

In which of the following situations would one use an independent t test?

A) A professor wants to know if one of his two Introduction to Psychology classes scored significantly higher than the other class on the same exam.
B) A professor wants to know if there was a significant improvement in test scores from Exam 1 to Exam 2 for one of his Introduction to Psychology classes.
C) An educator wants to know if students spend more time talking on the phone than studying during a typical day.
D) A researcher wishes to learn whether the oldest child in a family does significantly better on standardized tests than the youngest child in the family.