In a semiconductor, the effective mass ratio of hole to electron is 2:11 and the average relaxation-time ratio of hole to electron is 1:2. The ratio of hole mobility to electron mobility is
Mobility is $\mu=|q|\tau/m^*$. Electron and hole charge magnitudes are equal, so $\mu_h/\mu_e=(\tau_h/\tau_e)(m_e^*/m_h^*)=(1/2)(11/2)=11/4$. The smaller hole effective mass more than compensates for its shorter relaxation time. The ratio is 11:4, option D.
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