turn writer

[joham]

In China's classroom tests, we often meet with such fill-in sentences:

He has turned ____ (a, the, no article) writer. Then the answer is "no article".
But in the sentence: Both brothers have turned ____. Then is the answer writer, or writers? Well, you can't find such a sentence in a commonly-used dictionary.

Another question:
We say "Child as he is, he knows a lot." You can find similar sentences in dictionaries. But Chinese examination setters like to set such a question:

___(Child, Children, The children) as they are, they know a lot.
Again you can't find the answer from a dictionary.

Dear sir, could you please tell me which is the best answer. I feel I'm really hopeless at such exam questions.
I'm

[Tdol]

1 I am afraid that it is not a very natural sentence. We do use turn + profession without an article when someone leaves one profession and takes up a new one. In the question, I would use the plural.
2 I would use the plural without the article here, but it is again not a very natural sentence to me.