Step 1: Concept
Mridangam is a traditional South Indian percussion instrument. In the context of Ancient Tamil music, it was known by different names.
Step 2: Meaning
The question asks about the name Mridangam was known as in Ancient Tamil music.
Step 3: Analysis
Karuvi (A) is another name for a small hand drum used in South Indian Carnatic music.
Maddalam (B) is a large barrel-shaped percussion instrument from Kerala, also used in Carnatic music.
Murasu (C) refers to a type of gong or cymbal used in various South Indian musical traditions.
Muzhavu (D) was indeed the name given to the Mridangam in Ancient Tamil music.
The reasoning aligns with the correct answer, which is D. Muzhavu.
Step 4: Conclusion
Mridangam, as an instrument, had different names across various regions and periods of South Indian musical history. In Ancient Tamil music, it was known as Muzhavu.
Final Answer: (D)