If the cross elasticity of demand between two goods is highly positive, it indicates that the goods are strong ___, meaning an increase in the price of one leads to a surge in demand for the other.

Answer: substitutes

Cross elasticity measures how the demand for Good A responds to a price change in Good B. If the price of Coca-Cola rises, consumers will switch to Pepsi, causing Pepsi's demand to spike. This positive relationship defines substitute goods. Conversely, complementary goods (like cars and petrol) exhibit a negative cross elasticity, as a price hike in one reduces the demand for both.