In corpus-based studies of language change, what does tracking word frequencies over time help researchers identify?

• A. It reveals patterns of shift in usage.
• B. It reveals speaker's age exactly.
• C. It reveals grammar rules directly.
• D. It reveals phonetic features.

Answer: (D)

Tracking word frequencies over time shows how language use changes, revealing patterns of usage that rise or fall across periods. By watching which words gain or lose prominence, researchers can spot shifts in meaning, register, or topic focus as language evolves. This approach isn’t about pinpointing a speaker’s age, nor does it directly map grammar rules or phonetic features, which relate to demographics, sentence structure, and sounds respectively. So the key takeaway is that frequency trajectories illuminate patterns of shift in how language is used over time.