[CA11] Transducer Selection for aSeries MFD

I've recently purchased an a128 MFD and I'd like to purchase a transducer(s) for the Downvision and Chirp Sonar functions. However, I'm a bit confused with the requirements, given the range of transducers.

Do I need to purchase a separate transducer for the Downvision feature - and a second transducer for the Chirp Sonar feature? Or will one of the listed transducers work for both of these sonar features?

There are two Downvision transom mount transducers listed and one Chirp sonar transducer. I don't understand the difference between these transducers and what I would need for the MFD to function.