Question

in prehistoric times there were many volcanic eruptions in the oceans. lava spilled into the ocean waters, turning into igneous rock. this was followed by mass extinctions of many organisms attached to the ocean floor. what is the most likely reason for this?
a contact with the lava killed the organisms.
b the lava from the volcanoes took the oxygen from the air.
c in prehistoric times, there were very few organisms living in the oceans.
d the hot lava from volcanic eruptions changed the temperature of the ocean.

Explanation:

Option A is incorrect because benthic organisms attached to the ocean floor would not all directly contact the lava, which is localized as it cools into rock. Option B is wrong because lava interacts with ocean water, not atmospheric oxygen, to drive ocean extinctions. Option C is false as the question states there were mass extinctions of many such organisms, so there were not few of them. Option D is correct because large volumes of hot lava entering oceans would drastically raise water temperatures over wide areas, disrupting the stable, cold environments that benthic organisms depend on, leading to mass death.

Answer:

D. The hot lava from volcanic eruptions changed the temperature of the ocean.