Directions: Four alternatives are given for the idiom/phrase underlined in the sentence. Choose the alternative which best expresses the meaning of the idiom/phrase.

After careful consideration, he decided to sell his assets and invest in stocks, knowing very well that he was crossing the Rubicon.

The phrase 'crossing the Rubicon' refers to making an irreversible decision. 'Doing something that will cause his own downfall' refers to the phrase 'digging his own grave'. 'Preventing himself from performing to the best of his ability' refers to the phrase 'cramp his style'. The others are the incorrect meanings of the given phrase.