Answer:
Option C is the only correct answer.
Explanation:
We can see from the number line that a is to the left of zero, so it is negative. This means option A is incorrect.
Since b is to the left of zero, b is also negative. This means that -b is positive. Since c is to the left of zero, c is negative. Therefore, option B is incorrect: a negative number can never be greater than a positive number.
We see from the number line that a is less than c. Since both a and c are negative, this implies that -a > -c. Therefore, option C is correct.