Final answer:
In the market/data approach for property valuation, adjustments must be primarily made for the date of sale to account for changes in market conditions over time.
Step-by-step explanation:
When using the market/data approach to property valuation, adjustments must be made for a variety of factors. The principal factor for which adjustments must be made is the D. date of sale. This is because the real estate market can fluctuate over time, and values can change based on economic conditions, demand, and other real estate trends. Adjusting for the date of sale helps to ensure that the comparison between similar properties is fair and accurate, reflecting any changes in the market that may have occurred since the comparable sales occurred.