Answer:
d. He witnessed humans suffering from sickness, poverty, and death.
Explanation:
As he was a young Prince of India, he lived in an opulent and ordered palace, with his servants and his family. He was given all human and material goods to guarantee the best for him. However, his parents wanted him to hide the human side of life: suffering, violence, etc.
One day he was walking in the surroundings of the palace, close to the entrance, he saw a group of man carrying a dead corpse. He wondered what death was.
He was not used to seeing people cry or endure pain so he was strongly shocked. In reaction to this, he started a spiritual quest where he tries to see for all means what can be done in order to reduce human suffering.
As he came to understand there can be no existence without suffering since the essence of existence is suffering.
