Teacher's main task is to:

A teacher’s role is multi-faceted, requiring a combination of skills, knowledge, and personal attributes. The effectiveness of teaching depends not only on a teacher’s mastery of the subject but also on their ability to understand students and apply appropriate teaching techniques.

Key Points

•  A teacher's main task involves understanding students, mastering the subject, and acquiring teaching skills.
• Understanding students allows a teacher to adapt their teaching strategies to the learners' needs, interests, and abilities.
• Mastery of the subject ensures that the teacher can provide accurate, in-depth knowledge, which is essential for effective instruction.
• Acquiring teaching skills helps the teacher to present content in engaging ways, manage the classroom, and assess student progress effectively.
• All these components are crucial for successful teaching, making it essential for teachers to focus on all aspects of their professional development.

Hence, the correct answer is all of the above.