Correct Answer - B
Since a person can alight at any one of n floors. Therefore, the number of ways in which m pasengers can alight at n floors is
n
×
n
×
n
.
.
X
x
n
=
n
m
n
.
The number of ways in which all passengers can alight at different floors is
.
n
C
m
×
m
≠
.
n
P
m
.
Hence, required probability
=
.
n
P
m
n
m
=