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.
I think the answer is C and D
<span>How can a mutation in a DNA base sequence cause a change in a trait?</span>
Erythropoiesis is the formation of the red blood cells a process which takes place in the bone marrow. All blood cells are formed in the bone marrow, a soft, highly cellular tissue that fills the internal cavities of the long bones. It takes place in 8 stages where the first seven steps takes place within the bone marrow and after the 7th step the red blood cell is released into the blood stream as reticulocyte which then matures to erythrocyte after 1-2 days.
I believe the answer is a mutation.