If a certain strain of bacteria was called highly virulent what does this mean

In the context of gene for gene systems, often in plants, virulence refers to a pathogen's ability to infect a resistant host. ... Virulent can describe either disease severity or a pathogen's infectivity. The word virulent derives from the Latin word virulentus, meaning "a poisoned wound" or "full of poison.

Explanation:

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the answer is b.) hydrogen bonds between bases.

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