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OG-25 题
25. It can be inferred from the passage that the morphogent'tic determinants present in the early embryo are
(A) located in the nucleus of the embryo cells
(B) evenly distributed unless the embryo is not developing normally I
(C) inactive until the embryo cells become irreversibly committed to their final function
(0) identical to those that were already present in the unfertilized egg
(E) present in larger quantities than is necessary for , the development of a single individual :
The best answer is E. The socond and third paragraphs of the ; passage indicate that morphogenetic determinants are sub- , stances in the embryo that are activated after the egg has been fertilized and that "tell a cell what to become" (lines 15-16). If, as tb(; author asserts in the first paragraph, biologists have succeeded in dividing an embryo into two parts, each of which survives and develops into a normal embryo, it can be concluded that the quantity of morphogenetic detenninants in the early embryo is greater than that required for the development of a single individual. Choices A, B, and C are directly contradicted by information in the passage, and D makes an assertion that cannot be inferred from the passage.
答案为什么是E? 她给的解释不是很能读懂。 谢谢! |
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