1. Don't touch the food with your hand. I think it's so _______.
(Wound you name some suitable expressions for the blank?)
2. How many hours do you surf the Internet?
3. How many hours do you surf on the Internet?
(Which one is correct, #2 or #3?)
1 - gross, awful, dirty ...
http://thesaurus.com/browse/dirty
2 is better than 3. Both are correct, but 2 is more often used.