The right answer is: it´s twelve o´clock. The context in the sentence in Shakespeare´s Hamlet it makes us understand that Bernardo asks Francisco to go to sleep again, because it is too late to be awake, and "struck" refers to the clock´s chimes in the night.
The meaning of this sentence is <em>"It's twelve o'clock" (B).</em> This is written in old English which says the time of the day. By then, the clock uses a pendulum which sound each hour and count out the number the corresponding hour. Because of that the word ’strike’ was used with time during that age.
