The line including blank (5): "After the workshop, we ___ visit the library..." The word 'we' is a subject pronoun, the verb 'visit' is the main verb. In between (the blank in question) there is an auxiliary or modal verb (from the given options) that determines the mood or tense of the sentence. Option A: 'can' is a modal verb, it refers to possibility. When placed here it refers to the possibility 'to visit the library'. Hence it correctly fits the blank and A is correct. Option B: 'have had' is an auxiliary verb, it expresses the past perfect tense, referring to a past action that has been completed. The event in the sentence, however, has not yet taken place, hence it isn't a past even. Hence B is incorrect. Option C: 'be' in 'can be' is a verb (of the forms is, are, was, were). It means 'to exist', it is usually followed by a noun or its equivalent to express its existence. Here, the existence of nothing is expressed, hence C is incorrect. Option D: 'probably' is an adverb of certainty, it is placed between an auxiliary/modal verb and the main verb (we will probably, we can probably). Since there isn't any verb other than the main (visit), the adverb isn't a suitable option; D is incorrect.