If the mean of a normal frequency distribution of 1000 items is 25 and its standard deviation is 2.5, then its maximum ordinate is

A

$$ \frac {1000} {{\sqrt2\pi}} e^{25} $$

B

$$ \frac {1000} {{\sqrt2\pi}} $$

C

$$ \frac {1000} {{\sqrt2\pi}} e^{-2.5} $$

D

$$ \frac {400} {{\sqrt2\pi}} $$