An argument states: 'Our city's new recycling program, which focuses solely on plastics, is clearly a success because plastic waste in landfills has decreased by 20%.' What crucial unstated assumption does this argument rely on?

✓ Correct Answer: Option A

The argument assumes a causal link between the program and the waste reduction. Without this assumption, the decrease could be due to other factors, such as reduced plastic consumption or changes in waste management practices.