The answer would be D.
The reason so can be determined by taking a look at each option.
Option A would get us \(x^4 = m^2\), and wouldn't help us in anyway.
Option B would get us \({x^2\over m}=1\), and would only get us what the value of \(x^2\over m\), but that isn't what we are looking for.
Option C would get us \({x^2\over2}={m\over2}\), and would get us nowhere.
Option D would get us \(x = \sqrt{m}\), and get us the value of \(x\) in terms of \(m\), which is more helpful, and since \(x\) is normally the unknown or what we are trying to solve,
Option D is the best way to solve the equation \(x^2 = m\).