minlength , maxlength , required
Explanation:
First box: minlength
Second box: maxlength
Third box: required
The correct validation attributes are minlength, maxlength, and required. The input must accept a category abbreviation that is either two or three characters long. The minlength= " 2 " attribute enforces the lower boundary by preventing submission when the entered text contains fewer than two characters. The maxlength= " 3 " attribute enforces the upper boundary by preventing the user from entering more than three characters into the field. Since the question states that the input is mandatory, the required attribute must also be included. required is a Boolean validation attribute, so it does not need a value; its presence alone makes the field required before the form can be submitted. Together, these attributes configure basic HTML5 constraint validation directly in markup without requiring JavaScript. The completed input therefore requires a value, rejects values shorter than two characters, and limits the value to no more than three characters.
References/topics: HTML5 form validation, minlength, maxlength, required, text input constraints, mandatory form fields.