Step 1: Understanding the Concept:
The question asks for the specific reason why Akbar ascended the throne at the young age of thirteen. We need to find the information in the provided passage that explains this event.
Step 2: Detailed Explanation:
Let's analyze the passage for clues. The text states: "Akbar came back to India with Humayun. Soon, his father died."
The death of a ruling king (Humayun) would necessitate his heir (Akbar) taking the throne, regardless of his age. This directly explains why Akbar became king so young.
Option (A) is incorrect because while his father died, the term 'orphan' implies both parents are deceased, which is not stated. More importantly, the direct cause was his father's death, making him the successor.
Option (B) and (C) are not mentioned in the passage as reasons for his coronation.
Step 3: Final Answer:
The passage clearly states that Akbar's father, Humayun, died. This event led to Akbar becoming the king. Therefore, the correct answer is that he lost his father.