Consider the following statements about operations with rational numbers. I. When adding a negative and positive value, the sum is always positive.
II. When subtracting a negative value from a positive value, the difference is always positive.
III. When subtracting a negative value from zero, the difference is always positive.
IV. When multiplying a negative value by a negative value, the product is always negative.
V. When dividing a negative value by a positive value, the difference is always negative.
Which statements are true?