The statement that best explained the regulation of the genes should be when the chemical should be present. Therefore, the option A is correct.
Regulation of the genes:
Gene regulation refers to the process where the gene is to be off and on. At the time of early development, the cell should be started on the particular functions.
Also, it should be expressed at the specific time. Moreover, it help an organism for responding to the environment.
And, it should be off when the chemical is present in that.
Therefore, the option a is correct.
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