Final answer:
The punctuation in the sentence 'When the thunderstorm began we ran for shelter' is correct.
Step-by-step explanation:
The punctuation in the sentence 'When the thunderstorm began we ran for shelter' is correct. The sentence uses a comma to separate the dependent clause 'When the thunderstorm began' from the main clause 'we ran for shelter.' This is the correct use of punctuation when using 'when' as a subordinating conjunction. Additionally, the sentence ends with a period, which is appropriate to indicate the end of a declarative sentence.
Learn more about Punctuation in English sentences