Final answer:
The best cell style for a visual cue in a research report is bold and italicized, as it effectively highlights key information without being distracting.
Step-by-step explanation:
Among the cell styles listed for creating a visual cue in a research report, the use of bold and italicized text is most effective. This style draws attention to key points without overwhelming the reader, as might be the case with styles such as underlined and highlighted, or strikethrough and subscript which can be distracting. Bold and italicized text is particularly helpful for emphasizing important data or concepts, making it easier for readers to spot significant information.