C. High school needs to have a later starting time.
Explanation:
In the given passage, the author claims that high school needs to have a later starting time. They also provide arguments that support this claim - 70 percent of tardy high school students show up before the end of the first period, and most of them do it because they are sleeping in. School simply starts too early for them, and if it started later, they would arrive on time and probably perform better. That is not explicitly stated, but implied.
The rest of the options are not the claim, but the facts the author is providing. This is why option C is the correct one.
