Human activities in the recent past have caused the increased concentration of carbon dioxide in the atmosphere, but a lot of it does not remain in the lower atmosphere because of 1. its escape into the outer stratosphere. 2. the photosynthesis by phytoplankton in the oceans. 3. the trapping of air in the polar ice caps. Which of the statements given above is/are correct?

The correct answer is B because out of the three statements, only the second one accurately describes a significant mechanism that removes carbon dioxide from the lower atmosphere. Statement 1 is incorrect because carbon dioxide is a heavy gas and does not escape into the outer stratosphere or outer space in significant quantities. Instead, it tends to accumulate in the lower layers of the atmosphere. Statement 2 is correct. Oceans act as a major carbon sink. Phytoplankton perform photosynthesis, converting dissolved carbon dioxide into organic matter, which effectively removes large amounts of the gas from the atmosphere. Statement 3 is incorrect because while polar ice caps do trap small bubbles of air, this is a passive process that preserves a sample of the past atmosphere rather than acting as a continuous or significant removal mechanism for current excess emissions. Therefore, only statement 2 is a valid reason why a large portion of emitted carbon dioxide does not remain in the lower atmosphere.