定语从句,请问这句话怎么拆分成两句话?

题目

定语从句,请问这句话怎么拆分成两句话?
She showed the visitors around the museum,the construction of which had taken more than three years.
请问这句话怎么拆分成两句话?
这句话中的先行词是哪个？

答案

She showed the visitors around the museum.
The construction of the museum had taken more than three years.