The correct answer is Option A) after hearing a voice while meditating in a cave.
According to Islamic teaching, Muhammad PBUH stated to preach about worshipping the single God of the Jews and Christians after hearing a voice while meditating in a cave.
According to Islamic historians, the event ocurred in a cave outside the sity of Makkah called Hira.
The prophet used to go outside the city to meditate and relax.
On one of those occassions he heard a voice which scared and startled him. On enquiring, it was further revealed that the voice he heard was of Angle Gabriel. The same angel sent down by God to all prophets before him
After this occassion, he started to preach about the oneness of God in Arabia.
