During the modem boot process，how does the modem acquire the downstream channel？（）

• A、The modem is commanded by the CMTS to set to the specific channel
• B、The modem uses the default value in the broadcom chipset
• C、The modem tuner sets a level as defined by the DOCSIS specification
• D、The modem tuner scans the downstream spectrum until digital QAM modulated signal is encountered