Ratios of prompt D-meson yields ($\rm D_s^+$/$\Dzero$ and $\rm D_s^+$/$\Dplus$) as a function of $\pt$ in the 10% most central Pb-Pb collisions at $\snn=2.76 \rm TeV$ compared to the results in pp collisions at $\sqrt{s}=7 \rm TeV$. Statistical (bars) and systematic (boxes) uncertainties are shown.