What is the easiest way to separate hydrogen and oxygen out of a water molecule?
a.) boil the water until the chemical bonds break
b.) they cannot be separated by using physical properties
c.) filter the water using charcoal to break the chemical bonds
d.) use a magnet to pull out the metallic bonds

Option B, They cannot be separated by using physical properties

I'll go over why the other three options are wrong.

Option A - Boiling water would break the Intermolecular Forces between molecules (Essentially, the force that keeps water molecules stuck together will break, not the force that holds the atoms together)

Option C- Water isn't a mixture (Assuming that it's distilled), and so filtering it would do absolutely nothing.

Option D - There aren't any metallic bonds in water, only polar covalent bonds.

Thus, the only answer left is Option B.

Let me know if you need me to explain anything I mentioned here.
-T.B.