Question

the teacher had many complains _____Ravi.use preposition

Answer 1

Correct Answer for this sentence is `Against`

And New Correct Sentence will be :The teacher had many complains against Ravi.

As, When we talk about any complaint type, for any user, We ought to use against.

Hence, Your New Sentence with appropriate preposition is completed.

Against is a preposition commonly used for any types of quarrels/complaints for a particular member.  

Hence, In this sentence, We use against.

Thanks!