1. Why does the apex predator get the smallest portion of energy in the food pyramid?
A. nitrogen cycle
B. waste recycling
C. oxygen-carbon dioxide
D. water cycle
2. Which of the following cycles is not naturally occurring?
A. nitrogen cycle
B. waste recycling
C. oxygen-carbon dioxide
D. water cycle
3. How is the sun involved in the oxygen-carbon dioxide cycle?
A. It enables the photosynthesis to proceed.
B. It sustains the growth of organisms.
C. It heats up the surface of the earth.
D. It keeps the solar system intact.
