Final answer:
Ender learned from the older boys by c) observing and imitating them, a form of observational learning commonly used by children and animals to acquire new behaviors and skills.
Step-by-step explanation:
The character Ender in the context provided learned games and the older boys' character traits primarily by c) observing and imitating their actions. Observational learning is a fundamental way through which children and even animals gain new skills and knowledge.
Through this process, much like the hunter-gatherer children, Ender would watch and mimic the behaviors of those older than him as a method of learning, rather than relying on formal instruction or other means such as spying, asking for lessons, or reading diaries.