The correct answer is D$.$ SIFS.

Explanation:

Contention$-$based access is a method used in wireless networks to access the medium when multiple devices are competing for it$.$ In contention$-$based access, after a successful transmission, the device waits for a Short Inter$-$Frame Space $($SIFS$)$ before attempting to transmit again. SIFS is the shortest inter$-$frame spacing and is used for high$-$priority traffic, such as acknowledgments.

The other options are:

A$.$ DIFS $($Distributed Inter$-$Frame Space$)$ is a longer inter$-$frame spacing used before a device can transmit for the first time or after experiencing a collision.

B$.$ EIFS $($Extended Inter$-$Frame Space$)$ is used after a device experiences a transmission error or a collision.

C$.$ PIFS $($PCF Inter$-$Frame Space$)$ is used in Point Coordination Function $($PCF$)$ mode, which is a type of access method in wireless networks.

Therefore, the correct answer is D$.$ SIFS.