Help I don’t understand and I’m so confused and I’m doing online school please help 7-15

For questions 11-15

11. Magnesium Oxide is a combination between Magnesium and oxygen so the formula will be MgO

12. Calcium Chloride is a combination between Calcium and Chlorine, so the formula will be CaCl₂ the ₂ comes from the fact that there is two Chlorine atoms

13. Lithium Sulfide is a combination between Two lithium and a sulfur atoms,

so the formula will be Li₂S The ₂ coming from the two lithium atoms

14. Barium Selenide is a combination between Barium and Selenium so the formula will be BaSe

15. Aluminum Oxide is a combination between Aluminum and Oxygen, there are two Aluminum atoms and three Oxygen atoms, so it will make Al₂O₃

Hope this helps

it's c. (to reduce the greenhouse effect/carbon gasses)

this is a good question! i'll do some research and come back when i have the answer!