The answer is D its tightly packed cells allow for proctection against harmful substances.
It forms a chemical reaction and it starts bubbling
If you are conducting a study on the health of people who have been exposed vs not exposed, the method you should use to obtain data would be an observational study because it involves the pre-existing condition of the subjects.
The complementary stand is AACTGATCCGAT
The answer is 4, because if the ants smell the same dead smell on this particular ant in the colony, their initial reaction is to eliminate it. The chemical sprayed upon the ant acts as a stimulus for a particular behavior.
