Answer:
B. From another country.
Step-by-step explanation:
The term "exotic" is used to generally refer to something that is unusual, or is a foreign species, not native or locally found. It can be used to refer to things that are not from the local area and are brought from another place, usually a faraway land.
In the given context, the term "exotic" is used to refer to the plants that were "brought to the United States ... [and] thriving." This means that these plants like the kudzu were taken from another country and brought to be planted in the new land. The word "thriving" suggests that they are surviving in the new land, capable of prospering and growing.
Thus, the correct answer is option B.