professor holds office hours during final exam week and discovers much to his dismay that his sudden popularity affords him little time to engage in his favorite activity, watching cat videos. Sixteen students per hour arrive at his office and he patiently answers questions, averaging three minutes per student. On average, how long must a student wait in line to get their last $-$ minute questions answered?

?A $.$

$3$ ?minutes

?B $.$

$9$ ?minutes

?C $.$

$12$ ?minutes

?D $.$

$6$ ?minutes