The correct answer is "Cassius's response is unexpected because Brutus tried to protect him.". Taken from the play “The Tragedy of Julius Caesar” by William Shakespeare (1599), the situational irony in this excerpt explains that Cassius is surprised by Brutus response, since he did not manage to kill him right there as if it were expected. That is what situational irony describes: what is expected to happen and what actually does happen. In fact, the phrase “How ’scaped I killing when I crossed you so?” that Cassius says to Brutus reflects his surprise. Brutus does not attack Cassius because of his sorrow of having lost his wife, Portia, after she swallowed burning coals.