Your son is complaining that his smartphone is broken. He tells you that he cannot connect to the internet, nor can he make or receive phone calls and text messages. You ask him to start up music player on his phone and he is able to open it without any issues. It appears the common issue has to do with his device's network connectivity. Which of the following is MOST likely the problem with your son's phone?
A. The VPN password was entered incorrectly
B. Airplane mode is enabled on the device
C. The Bluetooth connection is disabled
D. The cellular radio in it is broken