Short Answer 
The key feature that marks the modern translation as an Old English poem is alliteration, a significant stylistic element of that era. Analyzing options such as alliteration, character, plot, and rhyme highlights alliteration as essential to understanding the poem’s historical context and literary tradition.
Step 1: Identify the Key Feature
The principal feature that indicates the original form of the modern translation as an Old English poem is alliteration. This literary device, which involves the repetition of the same initial consonant sounds in closely placed words, was a fundamental element of Old English poetry. Recognizing alliteration allows readers to appreciate the stylistic choices and historical context of the text.
Step 2: Analyze the Provided Options
To conclude which option best fits the question, we need to evaluate the available choices: alliteration, character, plot, and rhyme. While alliteration stands out in showcasing the poem’s Old English roots, the other terms do not significantly highlight this historical aspect. This analysis helps to eliminate less relevant options and reinforces the focus on alliteration as a defining characteristic.
Step 3: Refer to Examples and Conclusion
Examples from the text, such as the phrase “stubborn strife,” illustrate the use of alliteration effectively. These instances provide concrete evidence of why alliteration is the most fitting answer. Ultimately, recognizing alliteration not only enhances a reader’s understanding of the poem but also connects them to the rich tradition of Old English literature.