An essential characteristic of formative assessment is—

The correct option is: clarification of assessment criteria to the learners.

Step-by-step Explanation:

1. Understanding Formative Assessment: Formative assessment is an ongoing process used by teachers and students during instruction. Its primary purpose is to provide immediate feedback to adjust ongoing teaching and learning to improve students' achievement of intended instructional outcomes.
Unlike summative assessment, which evaluates student learning at the end of an instructional unit (e.g., tests and exams at the end of the year), formative assessment is diagnostic and developmental.

2. Analyzing the Options:
- "tests and exams at the end of the year.": This describes summative assessment, which is evaluative rather than formative.
- "clarification of assessment criteria to the learners.": For formative assessment to be effective, students must understand what is expected of them. Sharing and clarifying learning intentions and criteria for success enables learners to monitor their own progress and understand how to improve. This is an essential characteristic of formative assessment.
- "to focus on quantitative means to achieve objectivity.": Formative assessment relies heavily on qualitative feedback (descriptive comments, rubrics, and guidance) to help students improve, rather than just quantitative scores.
- "to assign relative ranks and positions to learners.": Ranking students is characteristic of norm-referenced summative assessment. Formative assessment focuses on individual learning progress and mastery rather than comparing students against one another.

3. Conclusion: Therefore, clarifying assessment criteria to the learners so that they can actively participate in their own learning process and self-assessment is an essential characteristic of formative assessment.