The structure that helps in the nutrition of the embryo is the yolk sac. The yolk sac is an important structure found in bird and reptile embryos, and it functions as a source of nutrition for the developing embryo. It contains stored nutrients, such as proteins and fats, that are necessary for the growth and development of the embryo until it hatches. The yolk sac is connected to the embryo through a structure called the yolk stalk, which transports nutrients from the yolk sac to the developing embryo. The yolk sac is eventually absorbed or discarded once the embryo has matured enough to obtain nutrients from other sources, such as the placenta in mammals. Therefore, in this question, the correct answer is option 1 - yolk sac.