A is the best answer. In the third paragraph, the author asserts that substances that function as morphogenetic determinants are located in the cytoplasm of the cell and become active after the cell is fertilized. In the fourth paragraph we learn that these substances are “maternal messenger RNA’s” and that they “direct, in large part, the synthesis of histones,” which, after being synthesized, “move into the cell nucleus” (lines 59-68). Thus, it can be inferred that after the egg is fertilized, the initial production of histones occurs in the cytoplasm.