Why can't do this small_____for me?I've helped you often eno

Why can't do this small_____for me?I've helped you often enough in the past.
A.command B.demand C.effort D.favour
A great celebration was held on his ______birthday
A.ninetys B.ninety C.ninetieth's D.ninetieth
Mike's mother bought him a new bike for his ____birthday
A.nibe B.the nine C.ninth D.the nineth