Final answer:
Report acceleration can be used in Normal search mode or Advanced search mode to expedite data processing. 'Accelerated search mode' is not a recognized search mode.
Step-by-step explanation:
To use report acceleration in a search engine or analytics platform, you must be in either Normal search mode or Advanced search mode. Report acceleration is not a search mode by itself; rather, it is a feature that can be applied within these search modes to speed up the processing of large datasets. Option 3, 'Accelerated search mode', is not a standard term used for search modes. So, the correct answer is: 1) Normal search mode or 2) Advanced search mode.
When you run an accelerated report, the search is executed against the acceleration structure rather than the original data.