A．To show that some species cannot be transplanted easily to new environments.
B．To give an example of rapid population growth that is not followed by decline.
C．To emphasize that species with rapidly growing populations harm ecosystem.
D．To introduce a study on the changing population size of certain species.
A．The availability of food is more important for species than the availability of space.
B．The amount of environmental resistance in an ecosystem does not change over time.
C．Environmental resistance controls the population size of species in an ecosystem.
D．The population size of most species increases at a constant rate.
A．They supplied an additional food source for gypsy moths.
B．They introduced gypsy moths to areas where there had been none.
C．They cleared oak trees from some areas where both animal species lived.
D．They manipulated the numbers of mice and oak's fruits in some areas.
A．Narrow down the topic of her article.
B．Read and revise her essay.
C．Provide some facts for her opinion.
D．Give her some advice on writing a paper.