Final answer:
The power button is used to shut off an emulated phone, not the volume up, home, or back buttons.
Step-by-step explanation:
The button used to shut off an emulated phone is typically the power button. This is the standard approach for both real and emulated devices. When you press and hold the power button, a menu will usually appear, giving you the option to turn off, restart, or put the device into airplane mode. Neither the volume up button, home button, nor the back button are designed for powering down the device.