If L $=[$c$,$d$],$ then the output of the statement $`$L$.$append$([$a$,$b$])`$ is:

$1$ point

$[$c$,$d$,[$a$,$b$]]$

$[$a$,$b$,$c$,$d$]$

$[[$a$,$b$],$c$,$d$]$

$[$c$,$d$,$a$,$b$]$