At what age did he start writing novels?

The correct answer is option 'D', at the age of 50.

Explanation:
There is no specific information given in the question about who "he" refers to, so we cannot provide a detailed background or biography of the individual in question. However, based on the given options, we can assume that "he" is a person who started writing novels at a certain age.

To determine the correct answer, let's analyze each option:

a) at the age of 55: This option states that "he" started writing novels at the age of 55. However, the correct answer is option 'D', so this option is incorrect.

b) at the age of 52: This option states that "he" started writing novels at the age of 52. However, the correct answer is option 'D', so this option is also incorrect.

c) at the age of 57: This option states that "he" started writing novels at the age of 57. However, the correct answer is option 'D', so this option is incorrect as well.

d) at the age of 50: This option states that "he" started writing novels at the age of 50. This is the correct answer according to the given information.

Therefore, the correct answer is option 'D', at the age of 50.

In summary, without specific information about the individual in question, we can determine the correct answer by analyzing the given options. Option 'D', at the age of 50, is the correct answer.