Answer:
D. Some have argued that the ability to communicate is a safety issue; I can assure you that most of the time this is not what is at stake.
Step-by-step explanation:
A good transitional sentence between two paragraphs should enable logical connection between the ideas conveyed through them.
The first paragraph states the author's support to the "zero tolerance" policy regarding use of the cell phones during school activities.
The second paragraph provides an example of excessive use of cell phones during a school orchestra performance that clearly wasn't an energency use.
So, logical connection would be the one introducing cell phone use a safety, emergency issue.