Option 1: 16 - This option suggests that Akbar was 16 years old when he became emperor. However, the correct answer is not 16.

Option 2: 19 - This option suggests that Akbar was 19 years old when he became emperor. However, the correct answer is not 19.

Option 3: 13 - This option suggests that Akbar was 13 years old when he became emperor. This is the correct answer. It implies that Akbar became emperor at a relatively young age.

Option 4: 10 - This option suggests that Akbar was 10 years old when he became emperor. However, the correct answer is not 10.

Therefore, the correct answer is option 3: 13. This means Akbar became emperor at the age of 13.