Which two statements are true about the digital audio in a VoIP network？ （）
- A Standard encoding techniques create an uncompressed digital data rate of 4000 bps.
- B Standard encoding techniques create an uncompressed digital data rate of 8000 bps.
- C Standard encoding techniques create an uncompressed digital data rate of 64，000 bps.
- D Voice quality is not a concern if compression is not used.
- E Two methods of quantization are linear and logarithmic.
- F Two methods of compression are u-law and a-law.