Answer:
He used peas because they are self pollinating,they grow fast,and they have many traits
Because the three-horned alien is heterozygous, we know that three must be dominant to four, because the gene for the three horns is "hiding" the gene for four horns. Therefore, the three-horned alien has the genotype Tt (T for three horns, and t for four horns). The four horned alien must be tt, because that is the only way that a recessive trait may be seen. If you solve the punnet square on a cross between Tt and tt, you end up with half three (heterozygous) and half four (homozygous recessive) it is a bit easier to explain with something a little "closer to home" if you want me to explain it again, just say so, I don't mind!
The reasoning behind this is because these unidentified plants could be used to cure diseases, used for food, and many scientists may even use these plants to create cosmetics. I really hope this helps and I just thought this off the top of my head so its may not be 100% accurate but its the basics of it.
Structure A is used for (4) cell communication. The cell membrance has receptros for cell communcation.
Structure B is used to (1) extract energy from nutrients. The mitochondria is the power house of the cell.
Structure C is used for (1) protein synthesis. The golgi apparatus is where protein is created.
