I'd say option 4, because all of those are capable of changing the enviroment
Answer:
part A is the answer
Explanation:
The tympanic cavity is an air chamber; it contains a chain of movable bones which transmit the vibrations of the tympanic membrane across the cavity to the middle ear.
Medications can be tested on cell cultures instead of being injected into patients unnecessarily.
Cancer cells continue to grow in the cultures uncontrollably allowing scientists to test multiple medications on the cancer cells.
