Final answer:
The correct answer is C. Trajan, 225, 300. Emperor Trajan increased the annual soldier's pay from 225 to 300 denarii during his reign from 98 to 117 CE, a time when the Roman Empire enjoyed significant prosperity and military success.
Step-by-step explanation:
In the 1st century AD, up to the time of the Emperor Trajan, the soldier's pay amounted to 225 denarii per annum, but the emperor raised this to 300 denarii. Therefore, the direct answer to the student's question is C. Trajan, 225, 300.
Emperor Augustus began the practice of institutionalizing a financial linkage between wealth and political power. While a senator needed an annual income of at least 1,000,000 sesterces to participate in the imperial government, a typical soldier made around 1,200 sesterces per year. During Emperor Trajan's reign, which lasted from 98 to 117 CE, he was well-regarded for his military successes and for being a 'good emperor'. His popularity and the empire's prosperity allowed him to make adjustments such as increasing the soldiers' pay from 225 to 300 denarii, enhancing their financial stability and, by extension, military effectiveness.
The financial pressures of the empire increased over time, with emperors like Diocletian having to implement reforms to stabilize the economy. Still, during the earlier times of Trajan, the soldiers saw a significant pay raise, reflecting the wealth and organizational structure of the empire at that time.