The amount of _____ has decreased.

• A. Beginning of Time
• B. Clean Water
• C. Fresh Air
• D. Soil Moisture

Answer: (B)

The idea being tested is how the usable portion of a resource can shrink over time due to human impact. Clean water isn’t just about how much water is there; it’s about how much of it is safe to use. Pollution from industry, agriculture, and sewage, plus overuse and groundwater contamination, reduce the quality of water so that less of it is considered clean and safe. Even if total water volume stays similar, the amount that meets safety standards can decrease, which is why “clean water” is the best choice here.

The other options don’t fit as a straightforward decrease in a usable quantity: the beginning of time is a fixed moment, soil moisture varies with weather and irrigation rather than steadily decreasing, and fresh air quality can improve in places with pollution controls even if it can worsen in others.