<p>Let's analyze the sentence:<br></p><p><strong>The chief executive wants to know [____ the final revisions will be made to the contract].</strong></p><p dir="ltr">The part wrapped with "[]" is a noun clause.<br></p><p>Let’s focus on the noun clause “________ the final revisions will be made to the contract.” First of all, (A) "on" and (B) "about" are eliminated because they are prepositions, and prepositions can’t be used to start a noun clause. </p><p dir="ltr"><span><span>(C) "</span><span>when"</span><span> and (D) "</span><span>which"</span><span> are possible answers since both of them are question words, and question words can be used to start a noun clause. But if (D) "</span><span>which"</span><span> is the answer, the article “the” after the blank needs to be removed. (C) "</span><span>when</span><span>" is the correct answer, and it fits the context. </span></span></p>