Which exception is exclusively available to teams under the Apron?

The answer is accurate because the Bi-Annual Exception is a special exception available exclusively to teams that are not above the apron. The apron is defined as a threshold $6 million over the luxury tax line, and teams that have not exceeded this threshold can utilize this exception.

The Bi-Annual Exception allows teams to sign a player for a maximum salary over two years. This exception provides financial flexibility for teams that may not have the full mid-level exceptions available while allowing them to maintain roster depth and continuity. Other exceptions, such as the Taxpayer Mid-Level Exception and the Room Mid-Level Exception, are designed for teams based on different financial standings, primarily revolving around the luxury tax limits and available salary cap space. Therefore, the Bi-Annual Exception stands out as the only option strictly provided to teams that are under the apron, verifying its exclusivity.