Concrete is one of the most widely used materials in the modern world, but its production is also one of the largest industrial sources of carbon dioxide emissions. Researchers are exploring several lower-emission alternatives: cements that require less heat to produce, mixes that incorporate industrial waste, and even bio-cements that use microbes to bind aggregates. None of these alternatives has yet matched conventional concrete's combination of cost and performance, but several are advancing rapidly.
Which choice best states the main idea of the text?
- A
Concrete production is environmentally neutral.
- B
Bio-cement is now standard.
- C
All concrete should be banned.
- Dcheck_circle
Researchers are pursuing several lower-emission concrete alternatives, none of which has yet displaced the conventional product.
Explanation
The passage's central claim is the active search for alternatives along with their current limits — B. A, C, and D contradict or overstate.