Scientists might predict that all of the following could happen due to solar flares:
- High-frequency radio waves used for radio communication will be blocked.
- Electrical systems in satellites will fail.
- Radio navigation systems and global positioning systems will be inaccurate.
- Power grid operations will go offline.
However, if you're looking for the most likely immediate impacts, the response that summarizes a common effect of solar flares is: radio navigation systems and global positioning systems will be inaccurate.
All of these responses are valid potential impacts of solar flares, but in different contexts and magnitudes.