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.
Presentation aids are visual methods of clarifying ideas and illustrating the message. So, your answer would be A.
Hope this helps!
The correct answer is 16 using the converse of the Pythagorean theorem
