Passage Summary: Some people want to put carbon dioxide into the ocean to stop global warming, but environmentalists are scared it will hurt the ocean; an engineer argues they shouldn't worry because the gas goes there anyway and does less harm than the warming would.

Conclusion: The concern that pumping carbon dioxide into the deep ocean would simply replace one destructive form of pollution with another is not justified.

Reasoning: Much of the carbon dioxide currently released into the air eventually migrates to the ocean naturally, and once there, it is less harmful than the effects of global warming.

Analysis: This is a classic 'Identify the Conclusion' task where the main point is a rebuttal to a previous claim. Look for the pivot word 'however,' which signals the engineer's stance against the environmentalists' worry. The final sentence provides the evidence, while the middle sentence containing the rebuttal serves as the primary conclusion. Focus strictly on the structure of the argument rather than evaluating if the engineer's science is actually sound.