An example of a double displacement is

A. AB-> A+B

B. AX+B - > A+BX

C. A+B - > AB

D. AX + BY - > AY + BX

D. AX + BY - > AY + BX

Explanation:

Double replacement:

It is the reaction in which two compound exchange their ions and form new compounds.

AB + CD → AC + BD

So from given list of reactions option D is correct while others are incorrect.

Other examples:

The reaction between sodium chloride and silver nitrate is double displacement reaction.

NaCl + AgNO₃ → AgCl + NaNO₃

The anion and cations of both reactants exchange. The anion of sodium chloride (Cl⁻) combine with cation of silver nitrate (Ag⁺) and form AgCl. While Anion of silver nitrate combine with cation of sodium chloride and form sodium nitrate.