The correct option is A X and Y are to be punished as it is immaterial whether illegal act is the ultimate object of the agreement or merely incidental to that object
2 people are said to have criminally conspired when an act is done in furtherance of a common object, given that there was common intention to commit such criminal act and it is immaterial whether the illegal act is the ultimate object or merely incidental to that object. X procured poison in furtherance of their conspiracy therefore, X and Y would still be liable and will be punished even if they were apprehended before administering the poison to Z.