Consider two physical quantities \( A \) and \( B \) related to each other as \( E = \dfrac{B - x^2}{A t} \) where \( E, x \) and \( t \) have dimensions of energy, length and time respectively. The dimension of \( AB \) is:
\( L^{0} M^{-1} T^{1} \)
\( L^{-2} M^{-1} T^{1} \)
\( L^{-2} M^{1} T^{0} \)
\( L^{2} M^{-1} T^{1} \)