A metropolitan transit authority plans to replace its entire fleet of municipal diesel buses with electric buses powered by lithium-iron-phosphate batteries, claiming that this transition will significantly decrease the city's overall net greenhouse gas emissions over the next decade. The authority points to studies demonstrating that electric buses generate zero direct tailpipe emissions, whereas the current diesel fleet contributes twelve percent of the city's overall transportation-related carbon output.
Which of the following statements represent necessary assumptions upon which the transit authority's argument depends? Select all that apply.
- The greenhouse gas emissions generated by the power plants supplying electricity to charge the new bus fleet will be lower than the tailpipe emissions eliminated by removing the diesel buses.Cevap
- BThe financial expenditure required to purchase electric buses and install charging infrastructure will be fully recouped through fuel savings over the next ten years.
- The total greenhouse gas emissions produced during the manufacturing and distribution of the electric buses will not exceed the operational emission reductions achieved over the ten-year period.Cevap
- DElectric bus technology will advance sufficiently over the next decade to increase single-charge driving range by at least fifty percent.
- EManufacturers of diesel buses will immediately discontinue production of internal combustion vehicles following the transit authority's procurement decision.
Cevap
The argument relies on two necessary assumptions: that upstream electricity generation emissions will not exceed the tailpipe emissions eliminated, and that emissions from manufacturing the electric buses will not outweigh operational emissions savings over the ten-year timeframe.
The transit authority claims that replacing diesel buses with electric ones will achieve a net reduction in greenhouse gas emissions over ten years. This claim moves from a premise about operational tailpipe emissions to a conclusion about total net emissions. To bridge this gap, two unstated conditions must hold true: first, the indirect emissions created by power plants to charge the batteries must be lower than the tailpipe emissions eliminated; second, the embodied emissions created during battery and vehicle production must not exceed the operational savings accrued over the ten-year window. Applying the Negation Test confirms that if either condition fails, net emissions will not decrease.
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Identifying Unstated Necessary Assumptions using the Negation Test
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