The correct answer is A. culminating.

The sentence should read: "It had been a trying afternoon, culminating at about six o’clock in the television breaking down."

Explanation:
- "Culminating" means reaching the highest point or a decisive moment, which fits the context of the sentence where the afternoon's events reached a peak with the television breaking down.
- "Leading" suggests a direction towards something but doesn't imply a peak or climax.
- "Arriving" doesn't fit well in this context as it suggests reaching a place rather than a peak moment.
- "Finalizing" implies completing or finishing something, which doesn't fit the context of the sentence as well as "culminating" does.