This doesn't say what the people who didn't study at all get. So this one is not true. That one is not true. Let's try this one. If one student studied for one hour more than another student, the student who studied more got exactly 15 more points on the test. Well, this is getting closer to the spirit of what the slope means, but this word exactly is what, at least in my mind, messes this choice up. Because this isn't saying that it's guaranteed that if you study an hour extra that you'll get 15% more on the test.