The Probability That a Poisson Random Variable X Is Equal $( 7 ! 2 ! ) / 9$

Multiple Choice

The probability that a Poisson random variable X is equal to 2, where = 7, is

A) $( 7 ! 2 ! ) / 9$ !
B) $9 ! / ( 7 ! 2 ! )$
C) $\mathrm { e } ^ { - 7 } 7 ^ { 2 } / 2$ !
D) $\mathrm { e } ^ { - 2 } 2 ^ { 7 } / 7$ !