Which belonged to a period of the "Five Good Emperors" and
helped ancient Rome reach its highest
point?

Answer; Trajan

Explanation;

I believe there are options but as they are not available this is the most plausible answer.

Caesar Nerva Traianus Augustus (Trajan) was a member of the Nervan-Antonine Dynasty and one of the so called Five Good Emperors. A decorated soldier, he was adopted by Emperor Nerva to be his successor and upon succession embarked on military conquests and annexations that saw Rome gain it's highest territorial expansion and thus its highest point.

On the home front, he also embarked on many construction projects in Rome including renovating the Circus Maximus. Upon his death he was deified by the Roman Senate and is commonly mentioned as one of the best emperors to rule Rome.

So good was his reign considered that succeeding Emperors on their inaugurations were wished to be Felicior Augusto, melior Traiano which means "more fortunate than Augustus [and] better than Trajan".

can you explain it better