I think the correct answer would be A. The yolk sac becomes the placenta. It is membranous sac that is attached to the embryo. It provides all the nutrition and the blood cells needed by the embryo. It is also called the umbilical vesicle.
The lac repressor protein is bound to the operator region of the lac operon when there is no lactose in the medium. When introduced in lactose, it binds to an allosteric site on the repressor causing its to change conformation and release from the operator. This allows the polymerase that is bound to the promoter region to proceed transcription of the lac operon genes (LacZ, Lac A, and Lac Y). Translation of these genes forms enzymes that enable the organism to break down lactose for energy.
The sun is the primary source of energy for living things mostly organisms like plants and ecosystems. But if you're talking about the bonds inside organic molecules, which are carbohydrates. With this, the energy from the sun gets trapped within a chemical bond and still relates to photosynthesis in plants.
If it is an animal like an eagle or one who preys on other animals it is a Carnivore, if it is an animal such as a cow or mouse it is herbivore, if it is a mushroom or other fungus it is decomposer, and if it is a plant like a tree or flower it is a producer.
