Which of the following, if true, would most undermine the effectiveness of the proposed strategy described in the passage for counteracting the greenhouse effect?

While this statement may provide context to the sources of carbon dioxide emissions, it does not directly address the effectiveness of iron fertilization. The strategy's success hinges on phytoplankton growth, which is independent of whether carbon emissions are industrial or natural.

Although measuring photosynthesis rates could be useful for monitoring the strategy's effects, it does not undermine the strategy itself. The ability to measure photosynthesis does not alter the underlying assumptions about iron deficiency and phytoplankton growth.

The discovery of new phytoplankton that require iron would reinforce the rationale for iron fertilization rather than undermine it. This finding may support the idea that iron plays a crucial role in the ecosystem, making the proposed strategy more relevant.

While this statement highlights natural carbon sequestration processes, it does not negate the specific effectiveness of iron fertilization. The proposed strategy focuses on enhancing phytoplankton growth to maximize carbon uptake, irrespective of other natural processes.