Final answer:
Option a uses proper punctuation with an em dash and a hyphen.
Step-by-step explanation:
The proper punctuation is used in option a. The sentence should be: The blond-haired boy loved the beach—until he was stung by a jellyfish. In this sentence, the em dash is used correctly to indicate a pause in the thought. The hyphen is used correctly to join two words that are being used as a compound adjective.
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