Which of the following pairs is not correctly associated?
a. killer t cells - attack and kill infected cells
b. t cells - activate killer t cells and b cells
c. b cells - engulf cells that are infected with pathogens
d. macrophages - consume pathogens and infected cells

Which of the following will not cause mass extinction? a. drastic change is weather b. geological change c. both a and b d. none of the above

Ascience research group is testing a new type of plant food. one trial is conducted in a controlled experiment. the data from the trial show that the plant that received the new food grew faster than the control plant. the group announces that the new plant food makes plants grow faster. what is the main weakness in this scientific claim?

What changes the stability of the element