Why cell theory is still a theory, not a scientific law?

The cell theory does not have enough support to become a law.  Cell theory is referred to as the history of scientific theory. All cells come from pre-existing cells, and that is the basic unit reproduction and a basic unit of all organisms. Cell theory did not become a law because the scientist who discovered it, did not give it a credit to become a law but a theory.  Hope this answer your question :)

it's c. (to reduce the greenhouse effect/carbon gasses)

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.