Final answer:
The CO2 concentrations will increase as there are now fewer trees to absorb it through photosynthesis.
Step-by-step explanation:
The CO2 concentrations will increase as there are now less trees absorbing it through photosynthesis. Trees absorb carbon dioxide through the process of photosynthesis, converting it into oxygen. With the clearing of 100 acres of trees for the shopping mall construction, there will be fewer trees to absorb CO2, leading to an increase in CO2 concentrations in the atmosphere.
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