The correct answer for the part of the grain in cereals where much of the protein lies is the aleurone layer.

1) Aleurone layer: The aleurone layer is located between the bran and the endosperm of a grain. It is rich in protein and contains enzymes that help to break down starch into simple sugars during germination. This layer is responsible for providing essential nutrients to the developing embryo.

2) Endosperm: The endosperm is the largest part of the grain and contains mainly starchy carbohydrates. It serves as a food reserve for the developing embryo.

3) Pericarp: The pericarp is the outer layer of a grain and is mainly composed of fiber. It protects the inner parts of the grain.

4) Embryo: The embryo is the small part of the grain that can develop into a new plant. It contains essential nutrients and is surrounded by the endosperm, which provides nourishment for the developing plant.

In summary, the aleurone layer is the part of the grain that contains a significant amount of protein, making it an important source of nutrition in cereals.