Antibiotics are best defined as:
AVitamins from yeast
BSynthetic chemicals that kill all cells
CVaccines against bacteria
DChemical substances produced by some microbes that can kill or retard the growth of other (disease-causing) microbes
Answer & Solution
Correct answer: D. Chemical substances produced by some microbes that can kill or retard the growth of other (disease-causing) microbes
**Antibiotics** = chemical substances **produced by certain microbes** (e.g., fungi like *Penicillium*, actinomycetes like *Streptomyces*) that **inhibit or kill other microbes**. The Greek 'anti'='against' + 'bio'='life' — but for humans they are pro-life (cure disease).
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