As an experienced technician, you are responsible for Technical Support. A customer calls to ask the best signal level and noise level for cell phone. How to respond?（）

• A、-40dBm signal and -90dBm noise
• B、-50dBm signal and -90dBm noise
• C、-30dBm signal and -90dBm noise
• D、-20dBm signal and -90dBm noise