Read the following two details from the article.
1. the company's products — like virtually every bulletproof backpack on the market are
advertised as meeting "ballistic level iiia" standards, which means they can withstand
bullets from handguns and revolvers.
2. furthermore, the products - which often are tested independently by the companies selling
them - are not vetted by the national institute of justice, an arm of the justice department
that certifies body armor for law enforcement officers.
which option best explains how these details develop a central idea of the article?
(a) the details explain why the companies that sell bulletproof backpacks often test their products
independently.
(b) the details describe two methods used to determine whether bulletproof products are effective in
protecting children.
(c) the details indicate that only bulletproof backpacks that have met certain standards can be advertised
as effective
(d) the details support the idea that there is no proof that bulletproof backpacks are effective in making
children safer.