正答

1. Origins, structure, and basic meaning

• Structure: 正答 (せいとう) can mean a correct answer or the act of answering correctly.
• Basic usage: 正答を一つ選ぶ selects the answer; 正答した人 modifies a person who answered correctly.

2. Common pitfalls and similar expressions

• Answer noun and verbal 正答した
  • The noun takes を as the selected item, while adding した creates an action modifying the respondent.