The exception in the principle protects a killing only when it happens without premeditation, in a sudden fight, in the heat of passion. The word doing the real work here is sudden, since it is what separates an impulsive reaction from a planned act carried out later.
Trace the timeline: the quarrel and threats happened at 7 pm, but X did not act in that moment. He walked back to his own shop, deliberately picked up a knife, and only then travelled to Y's residence, arriving at 9 pm, a full two hours after the original quarrel had ended. Fetching a weapon and covering that distance takes conscious, continued decision making, which is the opposite of an unplanned, sudden reaction.
That gap and that preparation are enough on their own to take this outside the sudden fight exception, regardless of whether X and Y had any history of enmity before that evening. Since the exception fails, the killing is treated as murder rather than as an excused sudden fight.
So the correct answer is X has committed murder.
Checking what fact would need to change for each option to be correct makes the timeline decisive.
Since the timeline already shows planning rather than suddenness, and none of the three alternative conditions actually change that, the option finding murder is the one that needs no unstated fact.
Therefore, the correct answer is X has committed murder.