Plants produce oxygen, energy (glucose).
Answer:
All viruses are obligate parasites; that is, they lack metabolic machinery of their own to generate energy or to synthesize proteins, so they depend on host cells to carry out these vital functions.
Pus is caused by dead white blood cells.
Most white blood cells self destruct after eating one pathogen.
Many pathogens flood into your knee when it gets cut.
Thus, many white blood cells try to eat the pathogen but get self destructed afterward.
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