Which of the following is a safety hazard of a 12-volt storage battery that lacks internal protection circuitry?
Why A lead-acid storage battery has very low internal resistance, so a short across its terminals can push hundreds or even thousands of amps through whatever bridges them. That current heats wires, tools or jewelry red hot in seconds, and the sparks can ignite the hydrogen gas that lead-acid batteries vent while charging, which is why a shorted battery can literally explode. The danger is the available current, not the voltage.
Watch out Twelve volts cannot push meaningful current through dry skin, so hand-to-hand shock is not the hazard; it generally takes on the order of 30 volts or more before shock becomes a real concern. RF from a nearby transmitter does not make battery electrolyte give off poison gas.
12 V won't shock you, but it will weld your wrench. Low voltage, huge current.