Answer:
I think that the answers are A and D.
For option A, we can come to the conclusion by thinking about the effects of invasive species. For example, when an invasive species appears in a specific environment and unfortunately feed on the same kind of plant as the native species, it will lead to the fact that they have to compete more in order to survive.
For option B, we can clearly see that it's wrong. From the point above, we can also predict that there is a high chance the invasive species will win the competition, resulting in the decrease population of the native specices that couldn't compete.
For option C, it is also impossible, instead the opposite is more likely to happen, because as we know, the native species, after a long period of evolution, became almost perfectly adapted to the environment, the appearance of invasive species may help the diseases that the native species weren't immune to spread faster, decreasing the population.
And I guess option D is obviously correct, no need to explain.
