I'm not completely sure, but I'm fairly certain that the answer is B.
Answer:
Layer A is the crust and Layer B is the mantle.
Answer: sunlight, carbon dioxide, and water
Explanation:
This happens in photosynthesis
The garden plants and snails stay balanced as they are still being eaten. However, if the cat is removed, the birds will overpopulate and then the snail would be eaten and decrease faster which gives garden plants an increase in population due to the decrease in snails. Hope this helps!