A list is defined using the following R command:

x$1=$list$(1$:$5,$ c$("$a$","$e$","$i$","$o$","$u$"),$ c$($TRUE$,$FALSE$),$ c$(1+4$i$,1-4$i$))$

Which of the following commands will return the output $[1]"$i$"$ when entered into the monitor

a$.$x$1[[2]](3)$

b$.$x$1[[3]][2]$

c$.$x$1[[2,3]]$

d$.$x$1[[2]][3]$