State one reason why a molecule may not be able to pass into or out of a cell.

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.

Checking blood sugar levels before, during, and after exercise is important for diabetics. select the best answer from the choices provided. t f

The best time to go swimming is: a. directly after eating b. when you are feeling rested and energetic c. when you are feeling tired and sluggish d. a half hour after eating