Answer:
D
Explanation:
Substitute goods are goods that can be used in place of each other for the same purpose.
Butter and margarine taste very similar, and are used for almost the same purposes (baking and cooking). They are a great example of substitute goods.
A car and a motorcycle are both modes of transportation. They are used for the same purpose, therefore are an example of substitute goods.
Oil and natural gas are both used as fuel, so they are another example of substitute goods.
A toothbrush and a toothbrush cannot be used in place of each other. In order to brush your teeth, you need both components. Therefore, this is the only answer choice that is not an example of substitute goods.
The best choice is D: toothpaste and toothbrush
