What did they use to sharpen tools in the old stone age?

Usually it could be either Rocks,Small stones or wood

dude you should crop your image so only the question shows. but   can you explain it better

world war i had a devastating effect on german-americans and their cultural heritage. up until that point   german-americans, as a group, had been spared much of the discrimination, abuse, rejection, collective mistrust experienced by so many different racial and ethnic groups in the history of the united states. indeed, over the years, they had been viewed as a well integrated and esteemed part of american society. all of this change with the outbreak of war.