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Which term defines one's age as measured in years? chronological age biological age social age mental age

Does anyone have an answer to this question? if so me.

Why do rna viruses appear to have higher rates of mutation? a) rna nucleotides are more unstable than dna nucleotides.b) replication of their genomes does not involve proofreading.c) rna viruses can incorporate a variety of nonstandard bases.d) rna viruses are more sensitive to mutagens.