The effect of the increase of carbon dioxide is plant productivity would increase because more carbon dioxide would be available for photosynthesis.
Photosynthesis is a process by which plants produce food with sunlight and water and carbon dioxide.
So, if the amount of carbon dioxide would increase in the atmosphere. The plants will increase the process of photosynthesis.
Thus, the correct option is B, plant productivity would increase because more carbon dioxide would be available for photosynthesis.
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