Answer : A,B,C
$L_1 :$
If $n>=0$ then the language $L_1$ contains ALL strings i.e. $L_1 = \{a,b \}^*$
if $n>=1$, the language $L_1$ contains ALL and ONLY the strings that start and end with $”a”$ i.e. Regular expression of $L_1 = a(a+b)^*a$
If $n>=k$, for some constant $k,$ the language $L_1$ contains ALL and ONLY the strings that start with $k$ $a's$ and end with $k$ $a's.$ i.e. Regular expression of $L_1 = a^k(a+b)^*a^k,$ where $k$ is some constant.
In any case, $L_1$ is Regular. Every regular language is CFL. So, $L_1$ is regular, as well as CFL.
In theory of computation, by default, range of any variable $n$ can be assumed to be $n>=0$. Since range of $n$ is not given in the question, So, we can assume it to be $n>=0$ (Some standard books of Theory of Computation mention that if nothing is mentioned about a variable $n$, then it can be assumed to be $n>=0$)
$L_2 :$
$L_2 = \{ wxw^R | |w| >0, |x| >0, w,x \in \{ a,b\}^* \}$
Every String, with at least 3 symbols, that starts and end with same symbol, is in $L_2$ (We can take $w$ as the first symbol, and $w^R$ will be the last symbol, remaining substring will be $x$)
Every string in $L_2$ has at least 3 symbols in it and starts and ends with same symbol(We can take $w$ as the first symbol, and $w^R$ will be the last symbol, remaining substring will be $x$).
So, $L_2 = [a\{a+b \}^+a] + [b\{a+b \}^+b] $
Since we have regular expression to describe $L_2,$ So, $L_2$ is Regular, as well as CFL.