An eyedropper is very small and can only hold a small amount. You can eliminate 2 from the start: millimeter and meter. These two are use for measuring distance not volume. ex.) I walked 2 meters. A liter is too big for an eyedropper. ex.) 1 liter of soda.
A glass full of juice would be 8 fuild ounces because a glass is basically a cup. A 8 gallons is too big, and a 8 tablespoons is too small. ex.) gallon of milk and tablespoon of sugar. 8 cups is too big because a glass is about 1 cup. 8 fluid ounces = 1 cup