Which factor would not limit the production of glucose by photosynthesis in plants?

The right answer is excess carbon dioxide.

For a cell to do a photosynthesis, it needs.

chloroplast

water (providing hydrogen and oxygen)

Carbon Dioxide (Providing Oxygen and Carbon)

And finally the sunlight.

This will produce, oxygen and glucose, two essential elements in animal life.

Excess of carbon dioxide.

Explanation: Excess of carbon dioxide present in the atmosphere does not limits the glucose production by the process of photosynthesis.

In fact the amount of carbon dioxide in the atmosphere is more than normal in the atmosphere and it does not affects the glucose production by  photosynthesis.

The plants needs oxygen, water, sunlight and chlorophyll for the synthesis of glucose by the help of the process known as photosynthesis.