Answer: The control group is the part where you see what happens when you change a variable you want to study/examine. Basically, you need the control group because you need something to see what happens when you change something.
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Answer:
(a) Waves P and Q have the same wavelength but wave P has twice the amplitude of wave Q.
(b) Waves Q and R have the same amplitude but wave R has twice the wavelength of wave Q.
(c) Wave T shows a steady frequency but changing amplitude.
(d) Wave S shows steady amplitude but a changing frequency.
e) Waves Q and R have a low amplitude and a steady frequency.
Answer:
Hydrogen Ions.
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Explanation: