If the price of good x rises and the quantity demanded of good y increases, then the two goods x and y must be.

To answer the question, we need to analyze the relationship between the price of good x and the quantity demanded of good y.

Step 1: Identify the scenario In this scenario, the price of good x has increased, and as a result, the quantity demanded of good y has also increased.

Step 2: Analyze the relationship Based on this information, we can infer that there is a positive relationship between the price of good x and the quantity demanded of good y.

Step 3: Determine the type of goods When the price of one good increases and the quantity demanded of another good increases, it suggests that the two goods are substitutes.

Therefore, in this scenario, goods x and y must be substitutes.