I want to subset a data$-$frame, df$,$ to include all columns, but keep only those rows which meet condition x$-$is$-$equal$-$to$-$y $($x and y are both columns within the data$-$frame$).$ Which code will accomplish this for me$?$

Group of answer choices

df$[$which$($df$x$==$y$),]$

df$[$which$($df$y$==$x$),]$

Either of the above commands will work

Neither of the above commands will work