What is an acidic cleaning agent primarily used for?

An acidic cleaning agent is primarily used for removing lime scale due to its ability to effectively break down mineral deposits, particularly calcium and magnesium-based scales that can accumulate in areas exposed to hard water. The acidic nature of these cleaning agents allows them to react with the alkaline components of lime scale, facilitating the cleaning process.

In contrast, the other options typically require different types of cleaning agents. For instance, window cleaning often involves a formulation designed to leave a streak-free finish rather than an acidic solution, while grease stains usually need a degreaser that targets fats and oils specifically. Sanitizing surfaces generally relies on agents with antibacterial properties rather than acidity to ensure effective microbial kill rates. Thus, the specific ability of acidic agents to tackle lime scale makes them the correct choice for that task.