Over the next 30 years, many countries are promising to move to net-zero carbon, implying that household emissions will have to be cut to close to nothing. A leading climate scientist reckons that, at best, half the reduction might be achieved through demand-side measures, such as behavioural changes by individuals and households. And even that would require companies and governments to provide more incentives to change through supply-side investments to make low-carbon options cheaper and more widely available.

Which one of the following statements best reflects the central idea conveyed by the passage?

Correct Answer: Low-carbon behaviour in people can be brought about by incentivising them.

Explanation:

To determine the central idea of the passage, let us analyze the core arguments presented by the author:

1. Household carbon emissions must be cut significantly to achieve net-zero carbon goals over the next 30 years.
2. At best, half of this reduction can come from demand-side measures (behavioral changes by individuals and households).
3. Crucially, achieving these behavioral changes requires companies and governments to provide incentives via supply-side investments that make low-carbon options cheaper and more accessible.

Connecting these points together, the passage emphasizes that individual behavioral change toward low-carbon choices depends heavily on incentives provided by governments and companies through investments that lower costs and improve availability.

Therefore, the option stating "Low-carbon behaviour in people can be brought about by incentivising them." perfectly encapsulates the central message of the passage.