In Florey and Chain's experiment, eight mice were infected with lethal doses of Streptococcus bacteria. The four mice given penicillin survived, but the untreated mice died. What can be concluded from these results? a. The experiment should be repeated with more mice. b. Penicillin can be used to treat bacterial infections in humans. c. There is a causal relationship between the use of penicillin and antibiotic resistance in bacteria. d. Penicillin may have played a role in the recovery of the four mice.

d. Penicillin may have played a role in the recovery of the four mice.

Explanation:

In the experiment performed by Howard Florey and Ernst Chain, they used the mouse protection test for the search of potential antibiotics. For this purpose eight mice were injected with a lethal suspension of bacteria and four of these mice were also given penicillin through injection. They observed that the four mice that received penicillin as injection were lived and all the rest mice died. On the basis of the observation made in this experiment they concluded that penicillin worked as an antibiotic against serious bacterial infections and thus those mice which have been given penicillin were alive.

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step-by-step explanation:

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