Answer:
it captures the sun's energy
B. Crystalline structure
C. Types of chemical elements
And
D. Amounts of chemical elements
If CO2 was in very small amounts then it would be the limiting factor of photosynthesis, this means the process will take place at a much slower rate because it is lacking one of the raw materials it needs for the process to occur. To find the optimum light intensity you really need all other factors to be at optimum levels or in abundance.
The make energy from sunlight through photosynthesis.