The correct option is
C 1 and 4 above
A sentence is in active or passive voice depending on whether its verb is in active or passive voice. A verb is in active voice when its form shows that the Subject does something or some action. A verb is in passive voice when something is done to the Subject. In other words, the Subject receives the action expressed by the verb. In passive voice, the doer of the action may appear in the phrase, "by .....". This could be one easy way of identifying a sentence in passive voice. However, in some cases, this phrase is omitted.
Let us look at the Subject in each sentence.
In 1), "The robber" is the Subject who was "beaten up" i.e an action was performed on him.
In 4), "The robber" is the Subject who "was caught". i.e. an action was performed on him.
Note that in both these sentences, the phrase "by the police" is used. This tells us that the police is the doer of the action. Hence, both 1) and 4) are in passive voice.
In 2), "The police" is the Subject, who performs the action "beat up".
In 3), "The robber" is the Subject, who performs the action "escaped".
Hence 2) and 3) are in Active voice.
Given the above, options A, B and D are incorrect. And option C is the correct answer.