Your pupil expands in dim light and contracts in bright light.
The major ingredient of scientific argument is scientific evidence and known science concepts. Thus through scientific idea, expectations and observations a scientific argument is given birth to. Scientific argument are usually arrived at by mean of scientific methods.
Answer:
Mutations in that organism, which can possibly lead to cancer (via mutations in the proto-oncogenes or tumor-suppressor genes)
I would say oxygen because respiration is breathing mechanically.
