In ancient Thailand, much of the local artisans' creative energy was expended for the creation of Buddha images and when they constructed and decorated the temples that enshrined them.

A. much of the local artisans' creative energy was expended for the creation of Buddha images and when they constructed and decorated the temples that enshrined them
B. much of the local artisans' creative energy was expended on the creation of Buddha images and on construction and decoration of the temples in which they were enshrined
C. much of the local artisans' creative energy was expended on the creation of Buddha images as well as constructing and decoration of the temples in which they were enshrined
D. creating images of Buddha accounted for much of the local artisans' creative energy, and also constructing and decorating the temples enshrining them
E. the creating of Buddha images accounted for much of the local artisans' creative energy as well as construction and decoration of the temples that enshrined them
I read many explanation about this question, but they all explain how to get the right answer by parallelism. My question is about answer B, can you explain in which they were enshrined? Which does in which refer? Which does they refer? why use passivity?
Thanks in advance.