Answer:
A. Introducing a new organism ALWAYS benefits the native organisms in an ecosystem.
Step-by-step explanation:
An invasive species refers to a species that is not native/indigenous to a particular area or ecosystem. As the name suggests, they "invade" the entire ecosystem by rapid growth of population and cause great harm and damage to the ecosystem.
Let us analyze each of the options.
A. Introducing an invasive species is not beneficial, rather it is very harmful to the other species of the ecosystem. Hence it is not a possible effect.
B. Due to rapid increase in population, the invasive species consumes more number of resources, thus it causes reduction in natural resources. Thus native organisms will be deprived of resources. Hence it is a possible effect.
C. As mentioned above, when there is a reduction in available resources, the natural organisms are deprived of food and nutrition, which causes decrease in their lifespan and ultimately causes death and eviction of the species. Hence it is also a possible effect.
D. Since the invasive species is introduced in the given area from an external source, there won't be any natural predators in the new area, so the species will thrive well and thus cause overpopulation. Hence it is also a possible effect.
The question asks for an effect that is NOT possible, so the required answer is A.