Which 2 gasses are involved with both the respiratory and the circulatory system? 1. Nitrogen and oxygen

2.oxygen and carbon dioxide
3. Oxygen ad urea

4.carbon dioxide and helium

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.