Why will a decrease in light intensity result in a decrease in the rate of photosynthesis?

1. A decrease in light intensity means a decrease in the available reactants needed for photosynthesis.
2. A decrease in light intensity means the enzymes that control photosynthesis may denature.
3. A decrease in light intensity means a decrease in the energy required for photosynthesis to take place.
4. A decrease in light intensity means an increase in the energy required for photosynthesis to take place.