<p>On closer inspection, several items were found to be faulty.</p>
<p>The correct answer is <strong>(C) inspection</strong>.</p>
<p>In this sentence, the word "inspection" is used as a noun to describe the action of examining or scrutinizing something closely. The phrase "on closer inspection" indicates that a thorough examination or inspection was conducted.</p>
<p>The other options are not correct:</p>
<p>(A) "inspecting" is a verb form, and it doesn't fit grammatically in the sentence as it doesn't match the noun phrase "on closer".</p>
<p>(B) "inspect" is also a verb form, but it doesn't fit grammatically in the sentence as it doesn't match the noun phrase "on closer".</p>
<p>(D) "inspector" is a noun referring to a person who carries out inspections. It doesn't fit in the sentence as it doesn't match the phrase "on closer".</p>