hope this helps
I do think that they close to not allow too much of either water or air from entering.
the hollow tube allows water to flow easily.
https://www.bbc.co.uk/bitesize/guides/z28g7p3/revision/1
1) A
2) B
3) C
4) D
5) E
6) F
7) G
8) H
The answers are already in the picture.
Answer:
Radio waves, microwaves, infrared and visible light can all be used for communication.