4. According to the passage， when biologists believed that the cells in the early embryo were undetermined， they made which of the following mistakes？
（A） They did not attempt to replicate the original experiment of separating an embryo into two parts.
（B） They did not realize that there was a connection between the issue of cell determination and the outcome of the separation experiment.
（C） They assumed that the results of experiments on embryos did not depend on the particular animal species used for such experiments.
（D） They assumed that it was crucial to perform the separation experiment at an early stage in the embryo’s life.
（E） They assumed that different ways of separating an embryo into two parts would be equivalent as far as the fate of the two parts was concerned.
5. It can be inferred from the passage that the initial production of histones after an egg is fertilized takes place
（A） in the cytoplasm
（B） in the maternal genes
（C） throughout the protoplasm
（D） in the beaded portions of the DNA strings
（E） in certain sections of the cell nucleus
6. It can be inferred from the passage that which of the following is dependent on the fertilization of an egg？
（A） Copying of maternal genes to produce maternal messenger RNA’s
（B） Synthesis of proteins called histones
（C） Division of a cell into its nucleus and the cytoplasm
（D） Determination of the egg cell’s potential for division
（E） Generation of all of a cell’s morphogenetic determinants