The answer is A. <span>effective length of the tube
In wind instrument, the effective length is not the actual length of the instrument but only the length that the finger holes manage to cover.
The more holes it managed to cover, the higher frequency of vibration it might able to produce, which lead to higher pitch of the instrument.</span>
If the the can prevent their live from hunting
Answer:
I believe it's the <em>collecting</em><em> </em><em>duct</em>
