Answer:
What can you catch but not throw?
I am a rock group with four members all of whom died in plane crashes. Who am I?
You use a knife to slice my head but you weep beside me when I am dead
I am commonly abbreviated to H
You cannot keep me until you have given me. What am I?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.