Final answer:
The distinction between primary and secondary authority is important for ensuring the legal support of tax positions to meet the 'substantial authority' threshold and to avoid penalties under Section 6662 of the Code. The correct answer is 'only a and b'.
Step-by-step explanation:
The distinction between primary and secondary authority is significant in legal research and writing because it relates to the strength and reliability of legal sources. Primary authorities are the law itself, including statutes, regulations, and case law, while secondary authorities are analyses, commentaries, or restatements of the law, such as legal encyclopedias, treatises, and law review articles.
Answer option (a) refers to the accuracy threshold of 'substantial authority', which suggests a need to rely on sources that have enough legal weight or persuasiveness to support tax positions. Meanwhile, option (b) refers to the avoidance of penalties under Section 6662 of the Code, which implies the use of sources that can shield one from penalties for taking an incorrect tax position due to a lack of substantial authority.
Accordingly, the correct answers would be option (d), 'only a and b,' as they are directly related to the use and implications of primary and secondary authorities in legal research and decision-making, particularly in tax law. Option (c) is about research techniques and does not directly relate to the distinction between types of authorities.