Water hardness and its practical ranges for domestic and laundry use Identify the correct set of statements about hardness classification and recommended ranges for different purposes.

Introduction / Context:
Hardness in water is caused primarily by calcium and magnesium salts. Classifying hardness ranges helps utilities and consumers understand scaling, soap consumption, and taste implications for household and public water-supply applications.

Given Data / Assumptions:

• Hardness expressed as ppm (mg/L) as CaCO3.
• Typical convention: soft, moderately hard, hard ranges used in water treatment practice.

Concept / Approach:
Practical guidelines often consider water up to about 75 ppm as soft; above roughly 200 ppm is hard and more likely to cause scaling. For laundry, low hardness minimizes soap consumption and prevents fabric dulling. For drinking, very low hardness can taste flat; a moderate range (about 75–120 ppm) is often acceptable for taste and mineral balance.

Step-by-Step Solution:

Verification / Alternative check:
Consumer guidance and water-utility references similarly bracket these values for residential expectations and appliance care.

Why Other Options Are Wrong:

• Each of (a)–(d) is individually correct; omitting any would give an incomplete picture.
• Thus (e) “All of the above” is the most complete statement set.

Common Pitfalls:
Confusing ppm as CaCO3 with mg/L of specific ions; always convert to CaCO3 equivalent for comparison.

Final Answer:
All of the above