OG4 阅读 Q29

Choice B is the best answer. In lines 60-62("When... cells."), the description of female goats' kids mentions that "some of them proved to be transgenic, the human gene nestled safely in their cells." The statement "some of them" indicates that while a number of the newborn goats were transgenic, others were not.
Choices A, C, and D are incorrect because the passage does not suggest that the female goats used in the initial experiment secreted antithrombin in their milk after giving birth, were the first animals to receive the microinjections, or had cells that contained genes usually found in humans.