Guess the missing item from this list: β-2, α-1, α-0, β-6, α-9, β-4, α-6, α-5, β-1, β-3, α-7, α-4, α-2, α-3, β-5, α-8.
Directly answer with only one item. Item format should match the list format. Provide no explanation. Answer format: "{item}."