______________ and ________________ gases are produced during normal battery operations. This gas mixture can explode if flames or sparks are brought near the battery.

The correct answer is hydrogen and oxygen. When a lead-acid battery is charged or discharged, a chemical reaction occurs that produces hydrogen gas at the negative terminal and oxygen gas at the positive terminal. This gas mixture can accumulate, particularly in a sealed environment, creating a potentially explosive atmosphere if flames or sparks are introduced.

The other choices do not relate to battery operations. Helium is a noble gas and does not participate in the chemical processes of batteries, while argon is primarily used as an inert shielding gas in welding and does not play a role in battery reactions. Propane is a flammable hydrocarbon and is unrelated to the gases produced in a standard battery's operation. Thus, the identification of hydrogen and oxygen as the gases produced during normal battery operations is critical for understanding the dangers associated with batteries, particularly in service or maintenance situations.