Which best explains why viruses do not have special structures or enzymes that allow them to make their own food? Viruses can use energy of living cells that they infect. Viruses can replicate inside a host that they infect. Viruses can cause contagious illnesses in host cells. Viruses integrate their RNA or DNA into infected cells.

Johannesburg kepler, an apprentice of brahe, believed in the heliocentric universe but rejected past astronomers belief in

This is a type pf behavior that animals are born with and them to survive

Which is an advantage of having memory cells when a pathogen is encountered for a second time. a) the memory cells are what proliferate into clones of cells in response to the binding of an antigen. b) memory cells are vital to the primary immune response in that they immediately recognize pathogens even at the first encounter. c) memory cells are essentially effector cells that are short lived and attack antigens even without having a receptor specific to that antigen. d) it ensures that more lymphocytes with a receptor specific to a particular antigen will be present than in a host that had never encountered that pathogen.