Answer:
Students whose Grades are low can sit For the exam Again .
We use whose to Introduce the relative clause when we are Referring to people or Things.In this Case,The Relative Clause talks about grades,Which is a thing that is why we use whose,We can Replace whose with the possessive pronoun Their .
In a sentence,The Relative Clause functions as an adjective because it is modifying the noun just like an adjective ,The Relative Clause - whose Grades are low- Is affecting the noun Students
<h2>Hope this helps you XD ✌️</h2>