Most of what we call "soil" is, by mass, simple mineral grains. The biology of soil, however, dwarfs its chemistry: a single teaspoon of healthy farmland soil contains more microbial cells than there are humans on Earth. These microbes drive nutrient cycles that determine whether the soil can sustain crops at all.
Which choice best describes the function of the second sentence in the text?
- Acheck_circle
It pivots the focus from minerals to microbial life with a striking quantitative claim.
- B
It introduces a new agricultural technique.
- C
It supports the first sentence's emphasis on minerals.
- D
It defines the term 'mineral grain'.
Explanation
"However" and the teaspoon claim shift the spotlight to microbes. B captures this pivot.