In the reaction mg(s) + 2h2o(l) --> mg(oh)2(s) + h2(g), what is the oxidation state of each h in h2(g)? a. +2 and –2 b. –1 and +1 c. +1 d. 0 no idea how to do this. i know its not d because that's for magnesium

The oxidation state of the atoms of any molecule in the element state equals zero. H2 is is the element state, therefore the oxidation state of the whole molecule equals zero and the oxidation states of the atoms also equals zero. Answer letter D is the correct answer. 
Magnesium has an oxidation state = zero before it undergoes the reaction and is oxidized. The oxidations state of the magnesium in Mg(OH)2 is +2.