Josh Richards is a musician I greatly respect.

who or whom

please help

Josh Richards is a musician whom I greatly respect.

Explanation:

Whom is used when you're replacing an object.

Who is used when you're replacing a subject.

But what's the difference between a subject and an object? Basically, think of reversing the sentence:

The subject of this sentence is I.  The object, then, is him. So we must use whom.

the answer is c) !