<span>It was 20 years between Muhammad's first revelation and when he conquered Mecca. The correct answer is C. His first revelation happened in 610 AD and he conquered Mecca 20 years later, in 630 AD. This first revelation refers to when the archangel Gabriel first appeared to Muhammad. And he defeated the Meccans in 630, taking control of their city, but he was quite generous towards them.</span>