Wood smoke contains dangerous toxins that cause changes in human cells. Because wood smoke presents such a high health risk, legislation is needed to regulate the use of open-air fires and wood-burning stoves. Which of the following, if true, provides the most support for the argument above? ['The amount of dangerous toxins contained in wood smoke is much less than the amount contained in an equal volume of automobile exhaust.', 'No significant beneficial effect on air quality would result if open-air fires were banned within the jurisdiction covered by the proposed legislation.', 'In valleys where wood is used as the primary heating fuel, the concentration of smoke results in poor air quality.', 'Smoke produced by coal-burning stoves is significantly more toxic than smoke from woodburning stoves.']