Choice "D" is correct. The more-likely-than-not standard involves a position that has a more than 50% chance of succeeding.Choice "c" is incorrect. The reasonable basis standard involves a position that is arguable but fairly unlikely to prevail in court. A numerical statement of this standard has at least a 20% chance, not a 10% chance, of succeeding.
Choice "b" is incorrect. The substantial authority standard involves a position that has a more than one-in-three chance, not a one-in-four chance, but a less than 50% chance of succeeding.
Choice "a" is incorrect. Reports issued by the U.S. Congress, IRS regulations, rules, and releases, and U.S. court case decisions, but not foreign court case decisions, constitute substantial authority for the substantial authority standard.