The option that best supports an idea in a discussion is A. evidence. Evidence provides tangible proof or support for a claim or idea. It is based on facts, data, research, or expert testimony. Arguments (B) can be used to support an idea, but they should also be backed up by evidence. Opinions (C) are subjective and may vary from person to person, so they are not the most reliable form of support. Interpretation (D) may be useful in analyzing evidence or arguments, but it is not a standalone form of support for an idea.
