Question

only the girl could be able to do it (re write the negative)
he is the best boy in the class (change into negative sentence)
as soon as he saw the tiger, he fled away (change into negative sentence)​

Answer 1

Answer:

Only the girl could not be able to do it.

Be is not the best boy in the class.

As soon as he saw the tiger, he did not flee away.

Answer 2

Answer:

Affirmative: Only he can play good cricket.

Negative: None but he can play good cricket.

Affirmative: Only the science students can apply for the post.

Negative: None but the science students can apply for the post.

Affirmative: Only they can do the work.

Negative: None but they can do the work