Which of the following best defines complementary goods?

Complementary goods are defined as products that are typically consumed together, meaning that an increase in demand for one good will lead to an increase in demand for the other. This typically occurs because the use of one good enhances or supports the use of the other, such as printers and ink cartridges. When the price of one good decreases, it can lead to an increase in quantity demanded, and consequently, the demand for its complementary good will also increase. Thus, choice B accurately captures the relationship between complementary goods: when the price of one good decreases, it makes it more affordable, thereby increasing its demand and the demand for its complementary good.

In contrast, the other options do not effectively represent the concept of complementary goods. Goods with similar attributes that can replace each other refer to substitutes, not complements. A lack of relationship between goods indicates that they are independent, which is not the definition of complementary. Lastly, saying that goods have a zero cross elasticity of demand would suggest that changes in the price of one good do not affect the demand for another, which contradicts the essence of complementary goods where they influence each other's demand dynamics.