Correct option is (b) initial state
To explain I would say: A deterministic finite state machine or acceptor deterministic finite state machine is a quintuple (Σ, G, s1, δ, F), where: Σ is the input alphabet (a finite, non-empty set of symbols), G is a finite, non-empty set of states, s1 is an initial state, an element of S, δ is the state-transition function: δ: G × Σ → G.