Answer: D.calculator and cell phone
Explanation:A complementary good is a good which can't be used alone or function without the associated good or paired good. If two goods are complementary this means using one of it will demand you to have the other good. For example for you to use an electric shaver you will need a charging cord for it to function , so they go together , they are complementary.
In order to ski , you will need your ski boots.
In order to paddle a boat you will need oar, which is a pole with a flat blade used for paddling a boat.
All these above are complementary.
Calculator and a cellphone on the other hand can work well separately , you can use one of them without the other.
