Which of the following statements correctly describes a difference between plant cells and animal cells?
a. plant cells have an envelope surrounding the nucleus. animal cells do not.
b. animal cells contain mitochondria. plant cells do not.
c. animal cells contain chloroplasts. plant cells do not.
d. plant cells are surrounded by a cell wall. animal cells are not.

80 points pls brainliest 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?