If a, b and c are three rational numbers, we have:

1. (a x b) x c = (a x c) x (b x c)
2. (a + b) x c = (a + c) x (b + c)
3. a x (b - c) = a x b - a x c
4. a x (b - c) = a x b - c

The product of a positive rational number and its reciprocal is:

1. 0
2. -1
3. 1
4. none