C. because the water erodes the rock away because it's jus sitting there gettig moist...like think about cereal wen it jus sits there in milk it gets moist and soggy
Get her something that lasts, but the question is how old are you? if you are between the ages of 5-10 a memorable picture of you two would be nice. 11-15 I would say a type of mug or shirt that says happy birthday. you could always get a card tho.
