4. when placed between oppositely charged metal plates, the region of a water molecule attracted
to the negative plate is the
hydrogen region of the molecule
geometric center of the moleculec
oh-oh plane of the molecule
oxygen region of the molecule

A) = Hydrogen region of water molecule.

Explanation:

We know that water consist of hydrogen and oxygen. There are two hydrogen atoms and one oxygen atoms in per water molecule. The both atoms are joined by the covalent bond. The bond between them is polar because the electronegativity difference between the hydrogen and oxygen is 1.24. The electronegativity of oxygen is 3.44 and hydrogen is 2.2.

Thus because of higher electronegativity of oxygen shared pair of electron attract more towards the oxygen and less towards the hydrogen. The oxygen becomes partial negative and hydrogen becomes partial positive.

When water molecules id placed between oppositely charged metal plates thus the negative charge is (partial negative oxygen) attracted towards the positive plates. while partial positive charge i.e, hydrogen is attracted towards the negative plate.

"the periodic table is arranged in order of atomic number."