What is the PC incremented by $4?$

$1.$ Each instruction is $1$ bytes long and the memory is byte$-$addressed

$2.$ Each instruction is $4$ bytes long and the memory is word$-$addressed

$3.$ Each instruction is $1$ bytes long and the memory is word$-$addressed

$4.$ Each instruction is $4$ bytes long and the memory is byte$-$addressed