The eastern gray squirrel is an invasive species in europe, where it typically outcompetes the native red squirrel. the graph below shows the population of red squirrels in an 125-acre forest in europe before and after the introduction of the eastern gray squirrel.

eastern gray squirrels were most likely introduced to the forest in
a. 1975//b.2010//c.2000//d.1985.

pine martens, a type of weasel, are a native predator of squirrels in europe. red squirrels have evolved adaptations against pine martens, but eastern gray squirrels lack such adaptations. efforts to increase the population of pine martens in the forest most likely began in
a.1985//b.2000//c.2010//d.1975.