A green box contains a blue box and a pink box. The blue box contains 2 H subscript 2 O. An arrow then leads in the green box to the pink box, which says 2 H subscript 2 O subscript 2. Lines lead from labels to parts of the boxes. Label A leads to the beginning of the green box. Label B leads to the blue box. Label C leads to the arrow. Label D leads to the end of the pink box. Identify each part of this chemical equation, which describes the breakdown of water into hydrogen and oxygen. A (the entire green box): B (the blue box): C (the arrow): D (the purple box):