Which of the following languages is regular?
$\left\{ww^R \mid w \in \{0, 1\}^+\right\}$
$\left\{ww^Rx \mid x,w \in \{0, 1\}^+\right\}$
$\left\{wxw^R \mid x, w \in \{0, 1\}^+\right\}$
$\left\{xww^R \mid x, w \in \{0, 1\}^+\right\}$
