Why is there a "none" option under rewards and how can I get rid of it?

Hi-

Once I add rewards to a fundraiser, a default "none" option is showing up - I can't understand why I would want to give someone the option to select that they don't want to support the fundraiser - if they don't they'll simply leave the page. In any case, the none option is added automatically and there doesn't seem to be a setting to get rid of it. Any ideas on how to have it not display?

Thanks,
Cynthia