The correct answer is $\boxed{\text{(C)}}$.
Let’s start by simplifying the given equation. We can factor out a $1/3$ from the third column of the matrix on the right-hand side, so we get:
$$\left[ {\begin{array}{{20}{c}} a \ b \ c \end{array}} \right] = \frac{1}{3} \left[ {\begin{array}{{20}{c}} 1&1&1 \ 1&{W_3^1}&{W_3^2} \ 1&{W_3^2}&{W_3^4} \end{array}} \right]\left[ {\begin{array}{{20}{c}} 1 \ {W_3^2} \ {W_3^4} \end{array}} \right]\left[ {\begin{array}{{20}{c}} {A} \ {B} \ {C} \end{array}} \right]$$
Now, let’s define a new matrix $M$ as follows:
$$M = \frac{1}{3} \left[ {\begin{array}{{20}{c}} 1&1&1 \ 1&{W_3^1}&{W_3^2} \ 1&{W_3^2}&{W_3^4} \end{array}} \right]\left[ {\begin{array}{{20}{c}} 1 \ {W_3^2} \ {W_3^4} \end{array}} \right]$$
Then, we can rewrite the equation as follows:
$$\left[ {\begin{array}{{20}{c}} a \ b \ c \end{array}} \right] = M \left[ {\begin{array}{{20}{c}} {A} \ {B} \ {C} \end{array}} \right]$$
This means that the sequences [p, q, r] and [a, b, c] are related by the matrix $M$. In other words, if we multiply the sequence [a, b, c] by the matrix $M$, we get the sequence [p, q, r].
Now, let’s look at the options. Option A says that [p, q, r] = [b, a, c]. This is not possible, because the first element of [p, q, r] is $p$, which is equal to $a$. However, the first element of [b, a, c] is $b$. Therefore, option A is not correct.
Option B says that [p, q, r] = [b, c, a]. This is also not possible, because the second element of [p, q, r] is $q$, which is equal to $b$. However, the second element of [b, c, a] is $c$. Therefore, option B is also not correct.
Option C says that [p, q, r] = [c, a, b]. This is possible, because the first element of [p, q, r] is $p$, which is equal to $a$. The second element of [p, q, r] is $q$, which is equal to $b$. And the third element of [p, q, r] is $r$, which is equal to $c$. Therefore, option C is correct.
Option D says that [p, q, r] = [c, b, a]. This is not possible, because the third element of [p, q, r] is $r$, which is equal to $c$. However, the third element of [c, b, a] is $a$. Therefore, option D is also not correct.
In conclusion, the correct answer is $\boxed{\text{(C)}}$.