To identify which synonym pair is NOT correctly matched, we need to assess each provided pair and determine if the words are true synonyms:
- Introduction - Preamble: Both words mean the beginning part of a text or speech, often used interchangeably. This pair is correctly matched.
- Collate - Assemble: Both refer to collecting or gathering items or information systematically. This pair is correctly matched.
- Improve - Ameliorate: Both words mean to make better or improve conditions. This pair is correctly matched.
- Stern - Step: "Stern" refers to someone being serious and unyielding, while "Step" refers to a stage in a process or movement in walking. These words have different meanings and are NOT synonyms. This pair is NOT correctly matched.
Thus, the synonym pair "Stern - Step" is not correctly matched.