Answer: C. Park naturalists are able to predict the eruptions of only five of the major geysers, including Old Faithful.
Step-by-step explanation: In writing, the term "elaboration" means to add more details. In the given paragraph we can see a description of the number of geysers that are in Yellowstone, and some details about them. From the given options, the one that provides elaboration and includes a specific example is the corresponding to option C, the elaboration is that park naturalists are able to predict the eruptions of only five of the major geysers, and the specific example is the "Old Faithful."