Final answer:
Information about whether LaRue took out a mortgage for the property purchase can most effectively be found by searching the county real property records, as these will detail property transactions and any associated liens or mortgages.
Step-by-step explanation:
The question pertains to where information about LaRue's property purchase and mortgage can be found. Among the options provided, b. County real property records are the most relevant source to search for information on property transactions and mortgages. These public records typically contain details about the purchase, ownership, and any liens or mortgages on the property. In contrast, a. LaRue's income tax return and c. LaRue's bank account transactions might provide some insights into LaRue's financial transactions or her ability to purchase such a property but are not likely to offer concrete evidence of a mortgage. Therefore, to specifically determine if LaRue took out a mortgage, McCloud should investigate the county's real property records.