What will the following code output?

const array $=[1,2,3]$;

const result $=$ array.concat$([4,5],6)$;

console.log$($result$)$;

$[1,2,3,[4,5,6]]$

$[1,2,3,[4,5],6]$

$[1,2,3,[4,5],[6]]$

$[1,2,3,4,5,6]$

Clear my selection