$S \rightarrow a S b \mid \in$

$E \rightarrow E+E|E * E|$ id

$S \rightarrow a S|S a| \in$

$S \rightarrow a S \mid \in$

$\angle\left(D_1\right)=\angle\left(D_2\right)$

$\angle\left(D_1\right)$ is a proper subset of $\angle\left(D_2\right)$

$\angle\left(D_1\right) \cap L\left(D_2\right)=\{\in\}$

$\left(L\left(D_1\right) \cup L\left(D_2\right)\right)^*$ consists of all strings in $\{0,1\}^*$ whose length is divisible by 3 .

$i+k=j+l$

$i=k$ and $j=l$

$i=l$ and $j=k$

$i+j=k+l$