Enables quick and efficient response to secondary exposure to antigen 2. : Kills cancer cells and virus infected body cells 3. : Forms antibody producing cells 4. : Absence results in no immune response 5. : Slows or stops the immune response

b tumor cells have a cell wall instead of a membrane

explanation:

tumor cells different from normal cells because tumor cells have a cell wall instead of a membrane.

69 is the correct math for the amino acids

answer: c. relative dating

relative dating uses the location and depth of where fossil is found in order to estimate it's age. it gives an idea about the order of past events. it does not give the absolute age but can give approximation. it just gives an indication about one fossil is older than other.