Answer
(a) to F
(b) to H
(c) to G
(d) to C
Work Step by Step
(a) to F
$(-3x)^{1/3}=\sqrt[3] {-3x}$
(b) to H
$(-3x)^{-1/3}=\frac{1}{\sqrt[3] {-3x}}$
(c) to G
$(3x)^{1/3}=\sqrt[3] {3x}$
(d) to C
$(3x)^{-1/3}=\frac{1}{\sqrt[3] {3x}}$