Consider the following language families:
$L_1 \equiv$ The context-free languages
$L_2 \equiv$ The context-sensitive languages
$L_3 \equiv$ The recursively enumerable languages
$L_4 \equiv$ The recursive languages
Which one of the following options is correct?
- $L_1 \subseteq L_2 \subseteq L_3 \subseteq L_4$
- $L_2 \subseteq L_1 \subseteq L_3 \subseteq L_4$
- $L_1 \subseteq L_2 \subseteq L_4 \subseteq L_3$
- $L_2 \subseteq L_1 \subseteq L_4 \subseteq L_3$