924 - Logical Reasoning

Question: Throughout the 1950's, there were increases in the numbers of dead birds found in agricultural areas after pesticide sprayings. Pesticide manufacturers claimed that the publicity given to bird deaths stimulated volunteers to look for dead birds, and that the increase in numbers reported was attributable to the increase in the number of people looking.
Which of the following statements, if true, would help to refute the claim of the pesticide manufacturers?

1. The publicity given to bird deaths was largely regional and never reached national proportions.
2. Pesticide sprayings were timed to coincide with various phases of the life cycles of the insects they destroyed.
3. No provision was made to ensure that a dead bird would not be reported by more than one observer.
4. Initial increases in bird deaths had been noticed by agricultural workers long before any publicity had been given to the matter.
5. Dead birds of the same species as those found in agricultural areas had been found along coastal areas where no farming took place.