Final answer:
A large-scale grain farm relying on an adjacent river for irrigation and drainage can cause damage to downstream plant and animal life.
Step-by-step explanation:
The subject of this question is Social Studies and it pertains to the externalities of a large-scale grain farm relying on an adjacent river for irrigation and drainage.
The correct answer to the question is: Damage to downstream plant and animal life. When the large-scale grain farm uses water from the river for irrigation, the runoff containing chemical fertilizers and pesticides can flow into the river, causing harm to the organisms downstream.
For example, if the river is the source of drinking water for nearby communities, the contamination could lead to health issues. Additionally, indigenous plant and animal species in the river may be negatively impacted by the pollution, disrupting the local ecosystem.
Learn more about Externalities of large-scale farming