Question

1. At the age of nine years old, he became too sick.

2. At the age of nine years, he became too sick.

3. At the age of nine, he became too sick.

4. At nine, he became too sick.

5. At nine years old, he became too sick.

6. At nine years old, he became too sick.

7. When he was nine years old, he became too sick.

8. Being nine years old, he became too sick.

9. Nine years old, he became too sick.
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Thank you for your help. I have posted several sentences. Which ones are not acceptable in terms of grammar?

Answer 1

4 is not acceptable. At nine WHAT? Nine o'clock?
8 is not, either. It makes it sound as if being nine years old is the cause of the illness.
9 is grammatically correct, but rather imprecise. The meaning is clear, but one must assume some missing words. "At nine years old, he became too sick" is better. "He was nine years old when he became too sick" is even better.