Final answer:
The flesh of a multicellular organism undergoes changes through transformation and adaptation to new conditions.
Step-by-step explanation:
In this question, the subject is biology. The options given describe how the flesh of a multicellular organism undergoes changes. Option 1 states that the flesh remains unchanged, which is incorrect. Option 2 states that the flesh transforms gradually, which is accurate. Option 3 states that the flesh adapts to new conditions, which is also accurate. Option 4 states that the flesh becomes rigid, which is incorrect. Therefore, the correct answers are option 2 and option 3.