Argument talks about pollution due to Gasoline-powered boat engines.
Gasoline-powered boat engines are pollutiing oceans.
1. In 1990, the government imposed stricter pollution controls on gasoline engines manufactured for boats
2. Beginning in 1995, the government imposed a program of inspections for pre-1990 boat engines with increasingly rigorous pollution standards.
3. As a result of evidence 2 this is happening: as the older boat engines fail to pass inspection, boat owners are increasingly retiring their old engines in favor of newer, less-polluting boat engines.
Pollution will decrease over next 10 years
IMO 3 is a cause and effect but still act as an evidence to the conclusion drawn.
So I am going with C.
SAID BUSINESS SCHOOL, OXFORD - MBA CLASS OF 2008