Identify the Modal in the following sentence :-

They needn't always make a complaint.

needn't

Here's why:

• A modal verb expresses possibility, necessity, probability, or permission.
• While "always" might be considered an adverb, it doesn't function as a modal in this sentence.
• "They" and "complaint" are nouns and pronouns, respectively, not modals.
• "Needn't" is a contracted form of "need not," which clearly expresses a lack of necessity for the action (making a complaint) on the part of the subject ("They").

Therefore, "needn't" is the modal verb in this sentence, indicating that making a complaint is not required or essential for the individuals mentioned.