Final answer:
Alco-pops or RTDs are pre-mixed alcoholic beverages that combine alcohol with flavored, often carbonated, mixers.
Step-by-step explanation:
The primary characteristic of 'Alco-pops' or RTDs (Ready to Drink) is C) They are pre-mixed alcoholic beverages. Alco-pops or RTDs are beverages that combine alcohol with flavored sugary mixers, similar to soft drinks. Similar to beer and sparkling wine, they often come in carbonated forms and are designed for convenience, marketed to consumers looking for a readily available alcoholic drink that's easy to consume.