$14)$ Which of the following is false? Justify your selected answer.

a$.100$ nlogn is O$($nlogn$/100)$

b$.($logn$)$ is O$($log logn$)$

c$.$ If $0<$ x $<$ y then nx is O$($ny$)$

d$.2$n $!=$ O$($n$*$k$)$