Which of the following is not equal to

Any negative number when raised to a power which is an even number, the result obtained is positive power of that number.

Any negative number when raised to a power which is an add number, the result obtained is negative power of that number.

So since in the question, the power is 4, the result of (-5)⁴ will be positive 4^th power of 5.

So the answer will be positive.

By looking at the option, Option C does not match to the desired result as the negative sign will persist in the result making it negative.

So option C does not match with the result.

So correct answer is C.