I really cant find it out. Its a homework question. I have looked through the internet and my science book
If you've tried new blades you probably need a new arm. Go to your local advanced auto or a place like that. Those guys are always standing around, being bored, waiting for people like you to come in so they can feel like real mechanics! :-) Good luck!
I am not sure that is a given conclusion. There is a lot of limestone, dolomite and gypsum in the world, and they are not clastic.
