Which bow cant be tied?

(a)  

What has 13 hearts but no organs?

(a)  

What gets sharper the more you use it?

(a)  

What teaches without talking?

(a)  

What goes up but never comes down?

(a)  

What fruit can never cheer up?

(a)  

What can fly but has no wings?

(a)  

What has 88 keys but cant open a door?

(a)  

What goes from z to a?

(a)