Application of a forward bias to a p-n junction

(a) Widens the depletion zone.

(b) Increases the potential difference across the depletion zone.

(c) Increases the number of donors on the n side.

(d) Increases the electric field in the depletion zone.

(c)

Number of donors is more because electrons from -ve terminal of the cell pushes (enters) the n side and decreases the number of uncompensated pentavalent ion due to which potential barrier is reduced. Then eutralised pentavalent atom are again in position to donate electrons.