Which of the following numbers is the largest?
$\text{(A)}\ 0.97 \qquad \text{(B)}\ 0.979 \qquad \text{(C)}\ 0.9709 \qquad \text{(D)}\ 0.907 \qquad \text{(E)}\ 0.9089$
Using the process of elimination:
Tenths digit: 
All tenths digits are equal, at $9$.
Hundreths digit:
$A$, $B$, and $C$ all have the same hundreths digit of $7$, and it is greater than the hundredths of $D$ or $E$ (which is $0$).  Eliminate both $D$ and $E$.
Thousandths digit:
$B$ has the largest thousandths digit of the remaining answers, and is the correct answer.  $A$ has an "invisible" thousandths digit of $0$, while $C$ also has a thousdandths digit of $0$.
$\boxed{\textbf{(B)}}$