Answer:
Secondary succession has happened.
Explanation:
secondary succession is the ecological succession that occurs after the initial succession has been disrupted and some plants and animals still exist. It is usually faster than primary succession
Symbiosis can vary between mutualism, parasitism, and commensalism, tho these grade into each other, it is often difficult to tell which is involved in a given relationship.
B. larger and more complex
Explanation: As the environment became more unpredictable, bigger brains helped our ancestors survive.
