The correct answer is: A. USB connection.
A Raspberry Pi can be powered by a variety of sources, but the most common is a USB connection. This can be from a computer, a power bank, or a wall adapter. The Pi also has a 5V GPIO pin that can be used to power it from a battery or other source. However, this is not recommended for long-term use, as it can damage the Pi.
Option B, internal battery, is not a viable option for powering a Raspberry Pi. The Pi does not have an internal battery, and even if it did, it would not be able to provide enough power to run the Pi for any length of time.
Option C, charger, is also not a viable option for powering a Raspberry Pi. A charger is designed to charge a battery, not to power a device directly. If you tried to use a charger to power a Raspberry Pi, you would likely damage the Pi.
Option D, adapter, is a possible option for powering a Raspberry Pi. However, it is important to make sure that the adapter is the correct voltage and amperage for the Pi. If the adapter is not the correct voltage, it will not power the Pi. If the adapter is not the correct amperage, it could damage the Pi.
In conclusion, the correct answer to the question “How power supply is done to RPi?” is A. USB connection.