Final answer:
To increase the alkalinity of swimming pool water, Sodium Bicarbonate (B) should be added. This base adjusts the pH up to the ideal range, as opposed to other listed chemicals which are used for different purposes or to lower pH levels.
Step-by-step explanation:
To raise alkalinity levels in swimming pool water, the chemical that should be added is B) Sodium Bicarbonate. This compound, also known as baking soda, is a base and can increase the pH level of the pool water. When sodium bicarbonate dissolves in water, it releases bicarbonate ions which can help to neutralize acidic substances in the pool, thereby raising the pool's pH closer to the ideal level of around 7.2.
Muriatic acid (hydrochloric acid) and sodium thiosulfate are typically used to lower pH levels, making them unsuitable for increasing alkalinity. Hydrogen peroxide is mainly used as a disinfectant and is not typically used to adjust pH. Proper maintenance of pool water involves regularly checking and adjusting chemical levels, including pH, to ensure the water is safe for swimming.