What is the main factor in the poor health of undeveloped countries?

a. too few doctors
b. more imports than exports
c. industrial pollution
d. infectious disease

Which list shows the levels of organization of an organism in hierarchical order from left to right, from the smallest to the most complex?

The earth's polarity has switched many times through history as evidence by what wh the earth clorets he has switched many times throughout history as evidence by what

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?