<p>Before being put on the market, all toy products are <strong>(A) thoroughly</strong> inspected for safety.</p>
<p>In this sentence, we need an adverb to describe how the toy products are inspected. The word "thoroughly" is the correct choice because it is the adverb form of the adjective "thorough." The adjective "thorough" means complete, detailed, or careful, and the adverb "thoroughly" means in a complete, detailed, or careful manner. Therefore, we use "thoroughly" to describe the action of inspecting the toy products.</p>
<p>The other options are incorrect:</p>
<p>(B) "Thorough" is an adjective, not an adverb, so it cannot modify the verb "inspected."</p>
<p>(C) "Throughout" is a preposition that means in every part or during the whole time. It does not fit the context of the sentence because we are not talking about the entire process of putting the toy products on the market, but specifically about the inspection process.</p>
<p>(D) "Through" is a preposition that means from one end or side to the other. It does not fit the context of the sentence because we are not talking about the physical act of passing the toy products through an inspection.</p>