What best describes ADPCM?

What best describes ADPCM?

A.
It stands for Advanced Duplicate Packet Code Marking.

B.
It specifies no transmission of data during silent periods of voice conversation.

C.
It allows synchronous data to be carried over voice card technology.

D.
It compresses voice from 64K per channel to 32K, 24K or 16K per channel.

E.
It compresses voice from 64K to approximately 8K.

Explanation:
ADPCM is a codec compression that takes a 64k voice stream and compresses it down to either an 32k, 24k, 16k stream.