Final answer:
Lauren may deduct all interest on the first loan and potentially all interest on the second loan if it was used for substantial home improvements. If the second loan's proceeds were not used as such, only a portion of that interest may be deductible.
Step-by-step explanation:
The question pertains to the deductibility of mortgage interest on a primary residence in accordance with U.S. tax laws. According to IRS regulations, homeowners can deduct interest on up to $750,000 of qualified residence loans (this limit is $1 million if the loan was taken out before December 16, 2017) used to buy, build, or substantially improve the taxpayer's home that secures the loan. In Lauren's scenario, she may deduct all of the interest on the first loan because the loan is less than or equal to $750,000. However, the interest deducted on the second loan depends on how the proceeds were used. If the proceeds were used to substantially improve the home, she may deduct all of the interest. If the proceeds were not used for home improvements, then based on the loan amount plus the outstanding balance of the first loan exceeding $750,000, a limitation would apply.
So, the correct statement regarding the deductibility of the interest Lauren paid in 2015 would reflect that, if the funds were used for substantial home improvement, she could potentially deduct all the interest paid on both loans, otherwise, the deductibility of the second loan's interest might be limited.