Final answer:
Snails growing shells and log decomposition have the common process of decomposition.
Step-by-step explanation:
The changes of snails growing shells and a log decomposing in the woods both have in common the process of decomposition (a).
Snails growing shells involve the deposition of calcium carbonate to form their shells, while log decomposition involves the breakdown of organic matter by bacteria and fungi.
Decomposition is an essential process for nutrient recycling in ecosystems.