What information is displayed by the command cat/proc/dma?

What information is displayed by the command cat/proc/dma?

A.
which DMA mode is in use

B.
general information about DMA on the machine

C.
whether DMA is enabled

D.
which DMA channels are in use

Explanation:
/proc/dma This file contains a list of the registered ISA direct memory access (DMA) channels in use. A sample/proc/dma files looks like the following:
4: cascade It shows whether DMA is enabled or not.