Base is defined as:

• A. A compound that produces hydroxide ions in solution and raises pH
• B. An acid that lowers pH
• C. A catalyst for digestion
• D. A disinfectant

Answer: (A)

Base means a substance that, when dissolved in water, releases hydroxide ions and raises the solution’s pH. This Arrhenius view explains why bases make solutions more alkaline. In wastewater work, bases are used to neutralize acidic streams and maintain the desired pH for equipment protection and process control; common examples include sodium hydroxide and lime. The other descriptions pertain to acids, catalysts for digestion, or disinfectants, which are not how a base is defined.