You have three identical p-n junctions; Junction 1 is unbiased , junction 2 is reverse biased and junction 3 is forward biased. From largest to smallest, rank the three junctions according to the magnitude of their diffusion currents.

In case of forward biased junction, the external electric field repels the electrons and holes towards the depletion layer, this increases the diffusion current. In case of reversed biased junction, the free electrons and holes are attracted respectively towards the positive and negative terminals of the p-n Junction. As a result diffusion current decreases.