Which factor most directly gave interlacustrine states both better farming and stronger armies?

1. The question asks for the one factor that served two purposes at once. 2. Iron technology produced hoes and axes, which raised agricultural output. 3. The same technology produced spears and other weapons, which strengthened armies. 4. That surplus fed a larger population and the weapons secured and expanded the state. 5. Good leadership and trade were also genuine factors, but neither delivers the farming and military gain through a single technology. _Source: NECTA ACSEE 2023 History 112/1, Question 2: Pre-colonial African Societies_