Which answer below correctly identifies the type of change and the explanation when potassium iodide and lead nitrate are mixed?

There are no choices provided, thus, I'll just tell you what happens when you potassium iodide and lead nitrite and you choose the best fit from the choices.

Potassium iodide and lead nitrite react based on the following equation:
  2KI + Pb(NO3)2 >  2K(NO)3 + PbI2 

As you can see, iodine and nitrite switched places in the products of the reaction (the products of the reaction potassium nitrite and lead iodide while the reactants were potassium iodide and lead nitrite). In chemistry, this is called a double replacement reaction.