If you have two Advertising 'How did you hear from us' options which are the same or similar i.e. Google and Gogle then it's possible to merge them together.
Click on General > Preferences > Customer Module > Hear From Us List > Pick the option you want to merge. Click on the little broom icon and pick the similar option from the drop down list. Click merge.
Please note, there is no way to un-merge these two options, so please be careful.