Most vaccines are derived from weakened or killed strains of the same virus that they prevent, unlike the derivation of smallpox vaccine from a different virus altogether.
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Athe derivation of smallpox vaccine from a different virus altogether
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Bsmallpox vaccine, which is derived from a different virus altogether
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Csmallpox's vaccine, which gets derived from a different virus altogether
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Dwhen smallpox vaccine is derived from an altogether different virus
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Ethe altogether different virus from which smallpox vaccine is derived
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正确答案: B