Final answer:
A cross-price elasticity of demand (Ecp) of 1.58 shows that the good is a substitute, as the positive value indicates that an increase in the price of one good leads to an increase in demand for the other good. Option A is correct.
Step-by-step explanation:
The cross-price elasticity of demand (Ecp) is a measure indicating how the quantity demanded of one good (Good A) will change in response to a price change of another good (Good B). A cross-price elasticity of 1.58, which is a positive value, signifies that the two goods in question are substitutes. This means that if the price of Good B increases, the demand for Good A will rise, suggesting that consumers are turning to Good A as an alternative to Good B. Therefore, a cross-price elasticity of 1.58 indicates that a good is a substitute good.