Final answer:
Building coal-fired power plants would not lower atmospheric CO₂ levels and would actually contribute to increased greenhouse gas emissions. Other options like planting trees and stopping deforestation help to remove CO₂ from the atmosphere.
Step-by-step explanation:
The activity that would NOT lower the amount of CO₂ in the atmosphere is building coal-fired power plants. When coal is burned, it releases significant amounts of CO₂, contributing to the greenhouse effect and climate change. In contrast, concentrating emitted CO₂ in large underground reservoirs, planting trees, and stopping deforestation are all strategies that would help to reduce CO₂ levels. Trees and plants perform photosynthesis, absorbing CO₂ and storing carbon in their structure, thereby acting as carbon sinks. On the other hand, deforestation removes these important carbon sinks, leading to higher CO₂ levels in the atmosphere
Approaches such as concentrating emitted CO₂ and planting trees play a role in what is known as climate change mitigation, whereas the construction of coal-fired power plants is contradictory to these efforts. Hence, out of the options provided, building a coal-fired power plant is the one that would not contribute to lowering atmospheric CO₂ levels.