The largest coral reef is the Great Barrier Reef, located in the Coral Sea, off the coast of Queensland, Australia
After studying the information you have given in the photograph, the element that will be formed when carbon-14 (14C) undergoes radioactive decay is nitrogen-14. You can also write it as just nitrogen. Either way is acceptable.
The population of the sub Sahara desert will grow in the years to come and has been growing for a while now. I know this because in the graph the line is climbing at the same crate constantly.