What is the value of 
\[1-(-2)-3-(-4)-5-(-6)?\]
$\textbf{(A)}\ -20 \qquad\textbf{(B)}\ -3 \qquad\textbf{(C)}\  3 \qquad\textbf{(D)}\ 5 \qquad\textbf{(E)}\ 21$
We know that when we subtract negative numbers, $a-(-b)=a+b$.
The equation becomes $1+2-3+4-5+6 = \boxed{\textbf{(D)}\ 5}$.
~quacker88