The group of words in bold, "where they were-and sometimes still are-used in ceremonial events," is a clause. Here's why:
1. **Independent Clause**: It contains a subject "they" and a verb "were-and are-used," making it a complete thought that can stand alone as a sentence.
2. **Subordinate Clause**: The clause "where they were-and sometimes still are-used in ceremonial events" provides additional information about the main idea in the sentence.
3. **Dependent Marker**: The word "where" at the beginning of the clause indicates that it is a dependent clause, as it cannot stand alone as a complete sentence.
4. **Function**: This clause acts as an adverbial clause, providing information about the location or circumstances of the origin of gongs.
Therefore, the group of words in bold is a clause in the context of the sentence provided.
