Which best describes Earth’s magnetic field lines?

What is a scientific theory? a. a scientist's guess about how something works b. the results of an experiment obtained using the scientific method c. a proven fact that will never change d. an idea that is backed by data from many sources

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

14. complete and balance the equations for the single displacement reactions. a. zn + pb(no3)2 -> b. al + niso4 -> 15. complete and balance the equations for the double displacement reactions. a. agno3(aq) + nacl(aq) -> b. mg(no3)2(aq) + koh(aq) -> 16. complete and balance the equations for the combustion reactions. a. __ ch4 + o2 -> b. __ c3h6 + o2 -> c. + o2 ->