Direct air capture machines pull carbon dioxide directly out of the atmosphere using chemical filters. The process can in principle help reduce atmospheric carbon levels, but the machines themselves require enormous amounts of energy. Whether direct air capture meaningfully helps the climate depends almost entirely on the cleanliness of the energy used to power it.
Which choice best describes the function of the third sentence in the text?
- Acheck_circle
It identifies a critical condition that determines whether direct air capture helps the climate.
- B
It rejects direct air capture as unworkable.
- C
It introduces a competing technology.
- D
It defines the term 'atmospheric carbon'.
Explanation
The sentence specifies the energy-cleanliness condition that makes the technology useful. B captures this conditional function.