From the languages below, which are context$-$free? Give short explanations.

a$.$ L $=\{(0^$n$)$ w $($w$^$R $)(0^$n$)$ : n $>=0,$ w in $\{0,1\}\}$

b$.$ L $=\{(0^$n$)(1^$j$)(0^$n$)(1^$j$)$ : n$,$ j $>=0\}$

c$.$ L $=\{(0^$n$)(1^$j $)(0^$j$)(1^$n$)$ : n$,$ j $>=0\}$

d$.$ L $=\{(0^$n$)(1^$n$)(2^$j $)$: n $<=$ j$\}$