Correct Option
Statement (d) is correct because statements (a), (b), and (c) present generalizations that are not fully supported or are directly contradicted by the information provided in the passage.
Incorrect Options
Option (a): The passage explicitly states, "It would be wrong, however, to conclude that introducing species to a region will inevitably cause a decline in species richness there." It further elaborates that some introductions, such as certain species from continental Europe to the British Isles, could potentially enrich local biotas. Therefore, the assertion that introduction of exotic species always leads to reduced biodiversity is incorrect.
Option (b): The passage indicates that while some introduced species have been responsible for "dramatic changes to native species and natural communities," it also notes that "Many introduced species are assimilated into communities without much obvious effect." This contradicts the claim that exotic species introduced by humans have always greatly altered native ecosystems.
Option (c): The passage explains that human actions have significantly increased the rate of homogenization by breaching natural dispersal barriers. However, it also acknowledges that homogenization can occur naturally, though restricted by "limited powers of dispersal." The statement that "Man is the only reason" for this conversion is therefore inaccurate, as natural processes also contribute, albeit at a slower pace.