Natural selection is always stabilising. When there is great selective pressure, it could look as if it is directional, but actually, the environment has changed so much that the entire ecological system is unstable, and evolution compensates and stabilises it. There’s no direction to this compensation, but more like throwing things at the wall and see what sticks.
Only in artificial selection is there a direction.
The answer is D, carbon dioxide, because carbon dioxide is used in photosynthesis. The answer is not b, glucose, because the end product of photosynthesis is glucose.
