From the natural number, as well as rational number, please define the relationship between the size

From the natural number, as well as rational number, please define the relationship between the size

Set of natural numbers n = {0,1,2,3...}
Set of integers z = {Z | z = ± n}
Set of rational numbers y = {y | y = N1 / N2, N2 ≠ 0}
The size of rational numbers can be compared by general division

If the rational numbers a and B make a + 1b − 1 = 0, then ()
A. A + B is a positive number, B. A-B is a negative number, C. a-b2 is a positive number, D. a-b2 is a negative number

∵ a + 1b − 1 = 0, ∵ a + 1 = 0b − 1 ≠ 0, the solution is a = − 1b ≠ 1, a, when B ＜ - 1, a + B is negative, so a option is wrong; B, because B ＜ - 1, so A-B is positive, so B option is wrong; C, because B ＜ - 1, a = 1, so B2 ＞ 1, a-b2 is negative, so C option is wrong; D, because B ＜ - 1, so B2, ＞ 1, a-b2 is negative, so D option is correct

The subtraction of two rational numbers is () a, positive number B, negative number C, zero D or more

The subtraction of two rational numbers is (all above D are possible)