Final answer:
Spain once had many Muslims but is no longer under Muslim dominance.
Step-by-step explanation:
The country that once had many Muslims but is no longer under Muslim dominance is Spain (option A).
During the Arab conquests in the early medieval period, Spain came under Muslim rule and was known as Al-Andalus. However, Muslim dominance in Spain ended in 1492 with the completion of the Reconquista, a centuries-long campaign by Christian kingdoms to recapture the Iberian Peninsula.
After the Reconquista, Spain became a predominantly Christian country and continued to be so throughout its history.