TOEFL Reading: ETS-TOEFL阅读机经 - CN86P3E8M24637IML$

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. Evolution is an unpredictable process because in mass extinctions highly-evolved organisms are exterminated. B. Evolution does not progress steadily to ever-higher levels of perfection because, as shown by mass extinctions, lineages favored by evolution can be suddenly replaced by those not favored previously when circumstances change. C. Catastrophes remind us that evolution is a process in which the best-adapted organisms are exterminated and their place taken by lineages shown to be poorly adapted. D. When mass extinctions exterminate the best-adapted organisms, less important lineages suddenly become better adapted and take their place.