The lungs and respiratory system work closely with the system to make sure oxygen reaches all the cells of our body. a) circulatory b) digestive c) integumentary eliminate d) nervous

Which statement is true about common childhood infectious disease? a. children should always be given antibiotics to treat an infectious illness. b. frequency of infectious illnesses usually increases as children grow older. c. having a minor infectious illness weakens a child's immune system. d. infectious illnesses are usually mild and require no medication.

What is the function of reverse transcriptase in retroviruses? a) it uses viral rna as a template for dna synthesis. b) it converts host cell rna into viral dna. c) it translates viral rna into proteins. d) it uses viral rna as a template for making complementary rna strands.

Viruses use the host's machinery to make copies of themselves. however, some human viruses require a type of replication that humans do not normally have. for example, humans normally do not have the ability to convert rna into dna. how can these types of viruses infect humans, when human cells cannot perform a particular role that the virus requires? a) the virus causes mutations in the human cells, resulting in the formation of new enzymes that are capable of performing these roles. b) the viral genome codes for specialized enzymes not in the host. c) the virus infects only those cells and species that can perform all the replication roles necessary. d) viruses can stay in a quiescent state until the host cell evolves this ability.