C because yoyo's are the oldest toy of the century but the prices goes up and down
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I don't think its necessary. do you?
I GOTCHUUUUU
I REALLY hope I can help you :)
The sentence which uses correct punctuation is C. In time, of course, all issues get resolved, but not necessarily in the way you would like.
In A, the comma before <em>he was concerned </em>should be a dash. In B, there should be a colon before <em>a flashlight, </em>not a semi colon. In D, there should be a comma before <em>yet, </em>and not a colon.