Which evidence from the text best supports the claim “although many people worked to fight smallpox, Jenner has been given credit for starting and spreading the practice of immunization”?

The claim says Jenner helped spread immunization, so the strongest evidence should show him sharing the vaccine with others. Choice D says Jenner sent vaccine to his medical acquaintances and to anyone who requested it, directly supporting that idea. The other choices describe an early inoculation, Jenner’s experiment, or the later replacement of variolation, rather than his role in spreading vaccination.

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