'यदा', 'कदा', 'सदा' — ये किस प्रकार के शब्द हैं?

उत्तर: (C) अव्यय — Avyaya (indeclinables) are words that do not change form regardless of gender, number, or case. Yada (when), Kada (when?), Sada (always) are kaalavachaka (time-indicating) avyayas.