An Ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the system through photosynthesis and is incorporated into plant tissue. By feeding on plants and on one another, animals play an important role in the movement of matter and energy through the system. They also influence the quantity of plant and microbial biomass present. By breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and other microbes.

I not that good with math but I would say C.
Answer:
the answer is 5
Step-by-step explanation:
5.3x5=26.5
So, personally I would take 252 and divide it by 4. this will give you 63 which is 1/4 of the cookies. Then add that 63 three times to get a total of 189 cookies which would be your 3/4 sold. so since there is only 63 cookies left then you would go into your final problem. 3/9 is equal to 1/3, so all you would do is divide 63 by 3 and get a total of 21 cookies given to the pta.