How has the Great Mosque at Cordoba been altered by Christians after the reconquest of Spain?

a. The interior arches were taken down to make a vast unified space
b. The mihrab was destroyed and an altar was placed in its stead
c. The interior was reroofed using European vaulting techniques
d. The building was turned into a church and then back into a mosque again

Ans: c. The interior was reroofed using European vaulting techniques