B) As the birthplace of Muhammad<span> and the site of </span>Muhammad's first revelation<span> of the </span>Quran<span> (specifically, a </span>cave 3 km (2 mi) from Mecca),<span> Mecca is regarded as the </span>holiest city<span> in the </span>religion<span> of </span>Islam<span> and a </span>pilgrimage<span> to it known as the </span>Hajj<span> is </span>obligatory<span> for all able </span>Muslims<span>. (wikipedia)</span>