In the lead-up to the 2007/2008 financial crisis, one strategy lenders used to maintain exposure to the performance of the loan pool was by retaining the "first-loss" or equity tranche of the securitized assets. This was the most junior tranche in a securitization, and was the first to absorb losses from defaults on the underlying loans. By holding onto this tranche, lenders kept "skin in the game" and aligned their interests with those of other investors. This was meant to incentivize responsible lending since lenders would be directly impacted by the performance of the loans.

B is incorrect. While it's true that some loan agreements might have included a provision allowing for the buyback of non-performing loans, this isn't typically how lenders maintained exposure to the loan pool in the context of asset-backed securities. In fact, having to buy back non-performing loans might represent a failure of the securitization process, which is intended to transfer risk away from the lender.

C is incorrect. Interest rate swaps are a type of financial derivative used to hedge interest rate risk, not to maintain exposure to the performance of a loan pool. While interest rate swaps might be used in the broader context of managing a securitized portfolio, they wouldn't directly align the interests of lenders and investors in the way the question implies.

D is incorrect. While a "vertical slice" approach could indeed represent a way for lenders to maintain exposure to the performance of a securitized loan pool, this approach wasn't the primary method used leading up to the 2007/2008 financial crisis. In a "vertical slice" approach, the lender maintains an interest in each tranche of the securitized assets, from most senior to most junior, hence bearing some of the risk if the loans default. However, the most common practice was to retain the first-loss or equity tranche, which is considered the riskiest part of the pool.