Scientists agree that ingesting lead harms young children. More lead paint remains in older apartment buildings than newer ones because the use of lead paint was common until only two decades ago. Yet these same scientists also agree that laws requiring the removal of lead paint from older apartment buildings will actually increase the amount of lead that children living in older apartment buildings ingest. Which one of the following, if true, most helps to resolve the apparent discrepancy in the scientists' beliefs? ['Other sources of lead in older apartment buildings are responsible for most of the lead that children living in these buildings ingest.', 'The money required to finance the removal of lead paint from apartment walls could be spent in ways more likely to improve the health of children.', 'Removing lead paint from walls disperses a great deal of lead dust, which is more easily ingested by children than is paint on walls.', 'Lead-free paints contain substances that make them as harmful to children as lead paint is.']