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 creation of Buddha images accounted for much of the local artisans’ creative energy as well as construction and decoration of the temples that enshrined them

IMO: A
they and them refer to antisans

NSNguyen wrote:IMO: A
they and them refer to antisans

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

They can refer only to Budha images.

a) artistians' is in possessive form.
b) temples modify 'decoration'