The exact extract asks which region currently has a carbon tax. The correct answer is C. European Union. In the Smart PV business context, carbon tax and carbon-pricing pressure are important commercial drivers because they push enterprises to reduce carbon emissions, adopt clean energy, and improve energy efficiency. The European Union has long been one of the most advanced regions for carbon pricing, emissions trading, and climate-policy enforcement. For Huawei Smart PV sales scenarios, this supports the value proposition of C&I photovoltaic systems: enterprises can reduce grid-electricity consumption, lower carbon exposure, improve ESG performance, and support green transformation. The other listed regions may have energy-transition initiatives or local climate policies, but the exam's intended answer is the European Union because it is the region most clearly associated with formal carbon-pricing pressure in the training context. Reference: Huawei HCSA-Sales-Smart PV V2.0 C&I Solution training extract.