Final answer:
The interaction between the Earth systems during a volcanic eruption involves the geosphere, hydrosphere, and biosphere. The lava affects the geosphere as it flows, alters the hydrosphere by changing a river's path, and impacts the biosphere by affecting ecosystems and human habitats.
Step-by-step explanation:
The Earth systems that interact during a volcanic eruption where lava flows down and blocks the flow of a river, causing it to change its path are the geosphere, hydrosphere, and biosphere. When a volcano erupts, the lava and ash interact with the Earth's surface, which is part of the geosphere. As the lava makes its way down the volcano into human habitation, it may block the flow of rivers, directly affecting the hydrosphere - the system that involves all water on Earth. Furthermore, the biosphere, which includes all areas where life exists, is impacted as the change in river path and the engulfing of habitable land by lava disrupt local ecosystems and human settlements.
The correct answer is B. hydrosphere, geosphere, and biosphere.