In which scenario would water softening be required?

Water softening is specifically designed to address the issue of water hardness, which is primarily caused by the presence of calcium and magnesium ions in the water. These minerals can create scale buildup in plumbing and appliances, leading to reduced efficiency and potentially costly maintenance issues. Softening water reduces these minerals, making it easier for soaps and detergents to perform effectively, thereby improving cleaning efficiency and extending the life of plumbing systems and appliances.

The other scenarios presented do not directly involve the need for water softening. Enhancing the taste of water often relates to other factors, such as dissolved solids or organic compounds, rather than hardness. Eliminating all bacteria from water is associated with disinfection processes, such as chlorination or UV treatment, rather than softening. Increasing the pH level of water involves treatment processes aimed at managing acidity or alkalinity, which differ entirely from the objectives of water softening. Therefore, the correct answer directly correlates with the primary purpose of softening, which is to mitigate the effects of hardness in water.