<p>The commerce department has launched a comprehensive investigation <u>in response to</u> allegations of accepting kickbacks in the construction sector.</p>
<div data-answer="c">(A) in violation of - This option suggests that the investigation is being conducted because the commerce department itself has violated something. This does not make sense in the given context.</div>
<div data-answer="c">(B) in addition to - This option suggests that the investigation is being conducted in addition to other ongoing investigations. However, the sentence does not provide any information about other investigations.</div>
<div data-answer="c">(C) in response to - This option correctly expresses that the investigation is being conducted as a response to the allegations of accepting kickbacks in the construction sector. This implies that the commerce department is taking action because of the allegations.</div>
<div data-answer="c">(D) on behalf of - This option suggests that the investigation is being conducted on behalf of someone else or another organization. However, the sentence does not indicate any such representation.</div>