Final answer:
The transaction that is NOT included in the definition of a residential transaction is dispositions of business interests involving property of five or more residential units.
Step-by-step explanation:
The transaction that is NOT included in the definition of a residential transaction is d. dispositions of business interests involving property of five or more residential units. A residential transaction typically refers to the buying, selling, or leasing of property intended for residential use. The other options mentioned in the question, including unimproved property intended for four units or less, agricultural properties of 10 acres or less, and leases with options to purchase residential property of four or less units, are all examples of residential transactions.