You had better ______ tonight.

- প্রদত্ত প্রশ্নে had better হচ্ছে modal auxiliary verb.

• You had better study tonight.
- এখানে had better হচ্ছে modal auxiliary verb.
- modal auxiliary verb 'Had better' এর পর verb এর base form বসে।
• structure:
- subject + had better/should/ought to/be supposed to + verb in simple form.

Source: Cliffs TOEFL.