OG4 阅读 Q22

Choice A is the best answer. Lines 9-11("Welcome... factories.") introduce the focus of the passage: "Welcome to the world of "pharming," in which simple genetic tweaks turn animals into living pharmaceutical factories." The passage then discusses the chronological development of "pharming," and describes ATryn, a useful drug produced after decades of laboratory experiments.
Choices B and C are incorrect because the passage does not primarily evaluate research or summarize long-term research findings. Choice D is incorrect because "pharming" is not a branch of scientific study.