I think a good addition to a collection of writing instruments that were unique to the twentieth century would be pens and pencils like we have now because back then they dipped feathers in ink and then wrote with them. They were very special because people wrote there feeling and grocery list and drew thing as art. And maybe more to add on would be paint brushes to make beautiful art like they did back then. I hope this helped u and that all your questions are answered.
Answer:
1. sound waves
2. eardrum vibrates
3. the bones in the middle ear amplify
4. the hair cells move up and down
Clarinet is a woodwind instrument...so, a)
