Final answer:
The Anglo-Saxon era begins in the year 449 AD, marking a period of significant cultural and linguistic development in England, including the creation of Old English.
Step-by-step explanation:
The Anglo-Saxon era is a significant period in English history which began after the Romans left Britain around 400 CE. The correct answer to when the Anglo-Saxon era begins is C. 449 AD. During this period, Germanic tribes known as the Anglo-Saxons, which included the Angles and the Saxons, settled in Britain. This era is noted for its unique cultural and linguistic contributions, including the Old English language, in which the epic poem Beowulf was written. The Anglo-Saxon kingdom was known for promoting learning and culture until the Norman Conquest in 1066.