3. Studying hard under g_ _ _ _ _ _ _ or support of the teacher is the key to academic success.

The missing word in your sentence seems to be "guidance". Here's the sentence with the missing word filled in:

3. Studying hard under guidance or support of the teacher is the key to academic success.

Here are the steps to achieve academic success under the guidance or support of a teacher:

1. Attend all classes: Regular attendance is crucial as it allows you to understand the course material and keep up with the lessons.

2. Participate actively: Engage in class discussions, ask questions, and share your thoughts. This will help you understand the material better and remember it longer.

3. Take notes: Write down important points during the lecture. This will help you remember what you learned and will be useful for revision.

4. Do your homework: Homework is designed to reinforce what was taught in class. Completing it will help you understand the material better.

5. Seek help when needed: If you're struggling with a topic, don't hesitate to ask your teacher for help. They can provide additional resources or explain the material in a different way.

6. Review regularly: Regular review of your notes and course material will help you retain the information and be prepared for exams.

7. Stay organized: Keep track of assignment due dates, test dates, and other important academic events. This will help you manage your time effectively and avoid last-minute cramming.

8. Take care of your health: Eat a balanced diet, get regular exercise, and ensure you get enough sleep. A healthy body contributes to a healthy mind, which is essential for academic success.