Classify each of the following as true or false, assuming that a, b, c, and d are whole nu...

Classify each of the following as true or false, assuming that a, b, c, and d are whole numbers. If a statement is false, give a counterexample.

a. If d|a and d|b, then d|(ax + by) for any whole number x and y

b. If da and db, then d(a + b)

c. If d|a2, then d|a.

d. If da, then da2