TOEFL Listening: TPO-TOEFL阅读TPO - 65ZRUQG3H27X0X1WN$

According to paragraph 5, once the Sun is in its "postnuclear" phase, the outer zone will differ from the inner zone in that the outer zone will A. undergo a much less dramatic change in size. B. maintain more nearly constant temperatures. C. cease to be a site of energy-generating activity. D. still contain some amount of hydrogen.