Consider the following relationships:
1. For each student who is about to take a 20-question exam, the number of questions that will be answered correctly versus the number of hours the student has studied.
2. For each student in a classroom taking a 20-question exam, the number of questions left to answer versus the number of questions already answered.
3. For each student who has taken a 20-question exam, the percentage of correct answers versus the number of correct answers.
4. For each student who has taken a 20-question exam, the number of correct answers versus the number of correct answers that the student was hoping to get.
a. Which one of the three relationships is perfectly positive?
b. Which one of the three relationships is perfectly negative?