extreme programming, as a system development methodology, emphasizes :

$1$

$.$

$$customer satisfaction

$2$

$.$

$$teamwork

$3$

$.$

$$communication as a core value

$4$

$.$

$$simplicity as a core value

$3$ and $4$ only, $23$ and $4$ only, $1$ and $2$ only, or $123$ and $4$