Which digit of $.12345$, when changed to $9$, gives the largest number?
$\text{(A)}\ 1 \qquad \text{(B)}\ 2 \qquad \text{(C)}\ 3 \qquad \text{(D)}\ 4 \qquad \text{(E)}\ 5$
When dealing with positive decimals, the leftmost digits affect the change in value more.  Thus, to get the largest number, we change the $1$ to a $9 \rightarrow \boxed{\text{A}}$.