❓ 题目 According to the passage, which of the following is a primary reason why some non-native species become invasive?
- A. A) They have a higher tolerance for pollution than native species.
- B. B) They lack natural enemies in their new environment, which helps control their populations.
- C. C) They are always larger in body size than native counterparts.
- D. D) They are introduced intentionally by humans for agricultural purposes.