Final answer:
Mary Musgrove was bilingual as evidenced by the text stating she served as an interpreter between English settlers and Creek tribes, requiring fluency in both languages.
Step-by-step explanation:
The textual evidence provided to infer that Mary Musgrove was bilingual is found in option D: "The text mentioned that Mary Musgrove often acted as an interpreter between English settlers and Creek tribes." This statement indicates that Mary Musgrove possessed the capacity to understand and communicate in both English and Creek, which is the definition of being bilingual. Being an interpreter requires one to be fluent in more than one language to accurately translate and convey messages between parties speaking different languages.