Read the excerpt from act i of hamlet.

bernardo: ’tis now struck twelve; get thee to bed, francisco.

what is the meaning of the underlined phrase?

this is twelve.
it’s twelve o’clock.
twelve things have fallen.
a man was hit twelve times.

The meaning of this sentence is "It's twelve o'clock" (B). 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.