Given the standard form:
[tex]\begin{gathered} 5\times10^{-4} \\ \end{gathered}[/tex]This can be expressef as a decimal by shifting the decimal point to the back 4 times (since the power is a negative 4) as shown:
[tex]\begin{gathered} 0.0005 \\ \end{gathered}[/tex]Hence the equivalent value for the standard form is 0.0005. Option B is correct