Buffers, MMU, cache and main memory

[K.I.L.E.R]

Guys, I need help with my *practice* exam.

A memory area that stores data between 2 devices or between a device an an application is known as:
MMU
DMA
buffer
main memory
secondary storage

I can rule out DMA, MMU and secondary storage.
I'd say it's a buffer, because main memory isn't popular due to performance reasons why 2 devices don't store their data to communicate with one another.

So is the answer "buffer"?

 

[K.I.L.E.R]

I found the answer btw.
I looked at the lecture notes and I am right.