Answer:
D. They created culture enrichment.
The correct answer is regression.
The child is regressing to a previous age when he used to wet the bed. He is now six years old, so he is supposed to be old enough not to wet the bed anymore, which was the case until his baby brother was born. Now the older child feels neglected and starts regressing to an earlier age in order to be noticed by his parents again.
For a long period of time, geneticists believed that one gene codes for one polypeptide. This hypothesis has been re-evaluated for two reasons. Firstly, some genes do not encode polypeptides, but functional RNA molecules. Secondly, due to the phenomenon of alternative splicing, some genes can encode several similar but not identical polypeptides. This phenomenon is present only in eukaryotes and it is based the fact that different parts of some genes can be used during gene expression.