Consider the following grammar G:
$S \rightarrow bS \mid aA \mid b$
$A \rightarrow bA \mid aB$
$B \rightarrow bB \mid aS \mid a$
Let $N_a(w)$ and $N_b(w)$ denote the number of a’s and b’s in a string $\omega$ respectively.
The language $L(G)$ over $\left\{a, b\right\}^+$ generated by $G$ is

$\left\{w \mid N_a(w) > 3N_b(w)\right\}$

$\left\{w \mid N_b(w) > 3N_a(w)\right\}$

$\left\{w \mid N_a(w) = 3k, k \in \left\{0, 1, 2, …\right\}\right\}$

$\left\{w \mid N_b(w) = 3k, k \in \left\{0, 1, 2, …\right\}\right\}$