Which type of water remains unaltered and contains dissolved minerals like calcium and magnesium?

The correct choice is hard water. Hard water is defined by its high concentration of dissolved minerals, specifically calcium and magnesium. These minerals are naturally occurring and contribute to the hardness of the water. Hard water can have various effects on other substances, such as making it difficult for soap to lather and potentially leaving mineral deposits on fixtures and hair.

In contrast, soft water has undergone a treatment process to remove these minerals, resulting in fewer dissolved minerals. Distilled water is water that has been boiled to create steam and then condensed back into liquid form, effectively removing impurities and most minerals. Tap water can vary in hardness depending on the source and treatment processes, but it may not necessarily contain high levels of calcium and magnesium like hard water does.

Therefore, the defining characteristic of hard water is its unaltered state with respect to these minerals, making it the accurate answer to the question.