Final answer:
The property tax for a home in the given city increases by $35 each year after 1990, starting with a base amount of $320 in 1990.
Step-by-step explanation:
The monthly property tax for a home in a certain city y years after 1990 is given by the formula $320 + $35y. By examining the formula, we can determine how the property tax changes over time. The $35y term implies that for each year y after 1990, the property tax increases by $35. The initial amount of $320 is the base property tax in the year 1990. Therefore, the correct answer to the question is that the property tax increased by $35 each year after 1990.