猜猜下面的英语谜语.
1.Whatlindofdogdoesn'tbiteorbark?
2.Whataroomhasnowalls,nodoors,nowindow,andnofloors?
3.Whathashandsbutnofeet,afacebutnoeyes,tellsbutnottalk?
4.Whatisblackwhenitiscleanandwhitewhenitisdirty?