Explanation
Correct answer: A.
Choice A is the best answer. “Afterward” logically signals that the events described in this sentence—the CEO’s public acknowledgment and apology—occurred after the rocket booster’s failure and are part of a chronological sequence of events.
Why the other choices are wrong
Choice B
Choice B is incorrect because “additionally” illogically signals that the events described in this sentence merely occurred in addition to the rocket booster’s failure. Instead, they occurred after the rocket booster’s failure and are part of a chronological sequence of events.
Choice C
Choice C is incorrect because “indeed” illogically signals that the events described in this sentence emphasize or strengthen a statement made in the previous sentence. Instead, they occurred after the rocket booster’s failure and are part of a chronological sequence of events.
Choice D
Choice D is incorrect because “similarly” illogically signals that the events described in this sentence are similar to the rocket booster’s failure. Instead, they occurred after the rocket booster’s failure and are part of a chronological sequence of events.