Astar gives off heat and light from the nuclear fusion reaction that takes place inside. what change happenes durning the nuclear reaction ?

hydrogen is changed to helium
hydrogen is changed to nitrogen
nitrogen is changed to hydrogen
helium is changed to hydrogen

Why are scientists concerned about the depletion of the ozone levels in the stratosphere?

Which of the following is a good strategy when it comes to desserts

20 point pls brianliest 1. what does a red shift mean? blue shift? 2. describe the big bang theory. according to this theory, how old is the universe? 3. scientists believe the universe is expanding. what is the evidence that supports this? 4. describe a nebula. 5. describe the 3 types of galaxies. what is a barred spiral galaxy? 6. what is a light year? how far is alpha centauri from earth? 7. describe the universal law of gravitation. be sure to include gravitational force between two objects. 8. describe the planets’ orbits around the sun. 9. what is the asteroid belt? where is it located? 10. describe rotation and revolution of earth. what determines an earth day and year? 11. how do galaxies exist? 12. compare and contrast the inner and outer planets. 13. what causes the seasons?