Write 0.4% as a fraction and as a decimal.
a.1/250=40.0
b.1/25=0.04
c.1/250=0.004
d.1/25=0.004

In order to convert percentage into decimal, divide the number by 100, 
so 0.4% = 0.004

& In order to convert into fraction, determine the denominator by divide decimal from 1, so 1/0.004 = 250
So, it would be: 1/250

In short, Your Answer would be Option C

Hope this helps!