Served as one of the most beautiful decoration of the church A. Painting
B. Murals
C. Stained Glass
D. Candelabras

Stained Glass is the technique used for the decoration of the church.

A stained glass is an artistic composition made of colored glass, painted or coated with enamels, which are assembled using lead rods.

This technique took on great relevance during the 13th century because it was used to decorate church windows because during this time (Middle Ages) the Christian religion was very important throughout Europe until the 15th century.

According to the above, the correct answer is C. because it mentions the decoration technique used by churches since the Middle Ages.

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can you rephrase the question? was there a picture to go along with it?