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