What percentage of the Earth's crust is made up of oxygen?
Clue: Earth's crust is made up of 28% silicon, 8% aluminum, and 17% other elements that are not oxygen.
Send answers to firstname.lastname@example.org
Parents may help, but try to let your child figure it out on their own.Weekly winner wins a Smencil. Monthly winner wins a $20 Barnes and Noble gift certificate!