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Can I say,
One day, when he went fishing, he felt the net was heavy. He thought that he had caught a big fish. When he pulled it up, he saw a wooden box inside the net.
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One day, when he went fishing, he felt the net was heavy. He thought that he had caught a big fish. When he pulled it up, he saw a wooden box inside the net.
Looks good to me
One day,while he was fishing, he felt the fishnet was heavy. he thought he had gotten a big fish. as soon as pulled up and check it. But there was a wooden box (OR how ever there wasn't a fish ).
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One day,while he was fishing, he felt the fishnet was heavy. He thought he had caught gotten a big fish. as soon as so he (quickly) pulled it up and checked it. But instead/in place of a fish there was a wooden box (OR how ever there wasn't a fish ).
could you explain why the as soon as is wrong??

advance thanks!
You could say
As soon as he pulled it up he checked it.
But you can't say
As soon as he pulled it up and checked it. You can't end the sentence like this!

As soon as he pulled it up and checked it, he realised that he had not caught a fish. Is ok.
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thank you very much
Would it sound better if I said ''but instead, disappointedly, he found it was only a big piece of wood.