A hydrogen bond connects . The figure shows five water molecules: four placed in the vertices of a tetrahedron, and the fifth – located at its center. Each molecule is represented by three closely packed spheres. Two equal spheres, representing hydrogen atoms, are connected by covalent bonds to a larger sphere that represents an atom of oxygen. The central molecule is connected to peripheral molecules by four hydrogen bonds. Two bonds connect the oxygen atom of the central molecule to the hydrogen atoms of two peripheral molecules, and two bonds connect the hydrogen atoms of the central molecule to the oxygen atoms of other two peripheral molecules. Each hydrogen bond has a minus sign marked near the oxygen atom and a plus sign marked near the hydrogen atom.

Use the accompanying figure to answer the following question.

A hydrogen bond connects .
an oxygen atom in one water molecule to an oxygen atom in another water molecule
the nuclei of adjacent water molecules
a hydrogen atom to another hydrogen atom
a hydrogen atom to an oxygen atom within a water molecule
a positive region of one water molecule to a negative region of another water molecule