What is the most suitable protection device to avoid electric shocks to human being in domestic power supply circuitry?

The most suitable protection device to avoid electric shocks in domestic power supply circuitry is a Residual Current Device (RCD), also known as a Ground Fault Circuit Interrupter (GFCI). It detects imbalances in electrical current, which can indicate a leakage to the ground, and quickly disconnects the electrical supply to prevent harm. RCDs are effective in protecting against electric shocks and reducing the risk of electrical fires. They should be installed in areas with higher risks, such as bathrooms and kitchens.