On page 94 it explains that The electrical resistance of germanium or silicon can be reduced to a very small fraction of its original value by combining either material with an extremely small percentage of a suitable impurity. In one type of combination, called negative,or N-type,the impurity causes the germanium or silicon to emit free electrons. Arsenic, bismuth, and antimony are suitable impurities for this purpose. In another type of combination, called positive,or P-type,the impurity causes the germanium or silicon to collect free electrons. Aluminum, indium, and gallium are suitable impurities to cause this effect.
It is asking what would cause it to emit free electrons not what causes it to collect free electrons. So the Answer is A. Bismuth