Measurement of $B(t \rightarrow Wb)/B(t \rightarrow Wq)$ at D\O

We report on a measurement of the ratio $R = B(t \rightarrow Wb)/B(t \rightarrow Wq)$. In the standard model this ratio is $> 0.998$ at the 95\% confidence level. Experimentally, we measure the ratio by noting the fraction of candidate events that have 0, 1, or 2 $b$-tagged jets.