The temperature dependence of the resistivity of a semiconductor is shown on page 389 of Modern Physics. This shows that answer (B) is correct. The resistivity appears to be inversely proportional to resistivity. The explanation for this is given on page 393 of Modern Physics: ``Only those electrons that have jumped from the valence band to the conduction band are available to participate in the conduction process in a semiconductor. More and more electrons are found in the conduction band as the temperature is increased, and the resistivity of the semiconductor therefore decreases."