The answer: Brain
In Angie's situation, she has her spinal cord intact but still has difficulty walking. Medically, balance, gait and walking require complete functions of the brain and spinal cord. Should her spinal cord and its nerves be intact, the problem lies with the other important factor which is the brain. The brain sends the signals to do any activity.
The last one. The only scenario where you wouldn't put a comma in the first quote is if it's a completed remark that uses particular punctuation such as a quotation or exclamation mark, but never a period. Hope this helped.
It might be said this paragraph shows "the damages caused by the lateral blast" (option D) because the reader gets to know that it can "shoot (..) pieces of rocks", "kill by impact, burial or heat" and to "knock entire forests". Nothing about prevention or causes is mentioned not even how to avoid it
