Answer:
The correct answer is: you activated the silent mode.
Step-by-step explanation:
The silent mode is an option most cell phone devices include and allows users to receive calls without others noticing it. What the silent mode does is to deactivate all the cell phone sounds such as ringtones, keypad tones or any other notification sound to avoid others hearing them. It is useful when an important call will be received and people are in meetings or public spaces.