Which term describes the phenomenon whereby unstressed vowels undergo systematic changes in pronunciation, such as 'o' sounding like 'a' in many positions?

• A Palatalisation
• B Voicing assimilation
• C Vowel reduction ✓
• D Consonant mutation

In standard pronunciation, unstressed 'o' and 'a' merge into a schwa-like sound in most positions, a phenomenon called akanye that is a hallmark of the Moscow norm.