Based on the information provided, we cannot definitively conclude that corals came into existence earlier than or later than single-celled eukaryotes, nor can we determine the current existence status of either group based solely on the elevation of their fossils. Fossil elevation could suggest past environmental conditions but does not directly indicate the presence or absence of the organisms today.
However, given that coral fossils were found at a higher elevation than those of single-celled eukaryotes, it might imply that the corals existed in a different ecological or geological context compared to the eukaryotes. Without additional information on the time periods represented by the fossils or the current status of each group, none of the conclusions provided can be validated or rejected.
In summary, the best conclusion we can derive from this context is simply an observation about the relative locations of the fossils, but it does not lead to any of the provided conclusions being definitively correct. Therefore, none of the options are appropriate conclusions.