If you look at each decimal place it is in decreasing powers of 10, ie...
after the decimal point in our number system you have columns with coefficient values of 10^-1, 10^-2, 10^-3, etc
1/10, 1/100, 1/1000 etc and in this case we have
4/10, 4/100, 4/1000, etc
So it would be C.
Technically the sequence is:
a(n)=(4/10)(1/10)^(n-1) if we are going to be talking about geometric sequences...