The major limitation is that C) he can not definitively show what causes the difference.
It may be caused by <em>something the people are doing</em> (if so, what?) or it may be caused by <em>some environmental differences</em> or a<em> combination of both</em>.
The half reaction with the the greater SRP has a greater tendency to gain electrons is the definition of reduction potential when considering a pair of half cell reactions.This reduction potential is measured against hydrogen electrode which is standard electrode.
<span>Movement of water from an area of lower solute concentration to an area of higher solute concentration</span>
