Iwill give 20pts, ! some fuel cells are powered by hydrogen. scientists are looking into the decomposition of water (h2o) to make hydrogen fuel with the of the sun’s energy. what challenge do scientists face with this task? a. decomposing water requires a high activation energy. b. the sun isn't a renewable resource. c. decomposing water results in toxic byproducts. d. scientists are uncertain what to do with the excess oxygen.

12) several teeth were found in an area of flat land covered with trees and plants. the teeth were examined by a paleontologist, and it was determined that the teeth came from a shark. they found many other shark teeth in this area. however, the people who discovered the teeth were puzzled, because there was no source of water near where the fossils were found. what is the paleontologist's best explanation for why the teeth were found in this area? a) sharks used to live on flat land. b) this area was once covered with salt water. c) this area was once covered with freshwater. d) someone buried the shark teeth deep in the ground.