As the given sentence has the word 'yesterday', we must fill in the blank with the past tense.
Option A - 'Seen' is used in perfect tenses with 'had/has/have', as we don't have any of these in the sentence, we can't use 'seen' here. Thus option A is incorrect.
Option C - 'Has seen' is incorrect. As the given sentence has the word 'yesterday', we can't use present perfect tense here. Thus option C is incorrect.
Option D - 'Will see' is used in the future tense. Thus option D is incorrect.
Option E - 'Had seen' is the past perfect tense to represent that the action was done before another action in the past. As the given sentence has only one action, we must use the simple past tense only. Thus option E is incorrect.
Option B - 'Saw' is the past form of the verb 'see' which can be used in the simple past tense. Thus option B is the correct answer.
'A policeman saw me crossing the street yesterday.'