17. what standard reduction electrode has a half-cell potential of 0.00 v? oxygen hydrogen lithium fluorine

I believe Hydrogen is the standard reduction electrode that has a half-cell potential of 0.00 V. In electrochemical cell, an electric potential is created between two dissimilar metals. This potential is a measure of the energy per unit charge which is available from reduction or oxidation reactions to drive the reaction. 

C. which metal is less dense