TOEFL Listening: TPO-TOEFL阅读TPO - 7ISEDCXWUHBN7UXTN$

In paragraph 1, why does the author point out that stars are billions of years old? A. To establish that starlight is produced by an ongoing process and not by a one-time event. B. To suggest that stars contract much more slowly than was previously believed. C. To argue that shrinking cannot be the main way stars generate energy. D. To argue that fusion in a star slows down as quantities of heavy elements build up.