<p>Let's analyze the sentence:<br></p><p><strong>Employees (who will be assigned to work overseas) are advised to study the language of the country (in ___ they will reside).</strong></p><p>The part wrapped with "()" is an adjective clause.</p><p dir="ltr"><span><span>Let’s focus on the adjective clause, “in _______ they will reside.” The blank should be filled with a relative pronoun to refer to the antecedent “the country.” The correct answer is (D) "</span><span>which"</span><span>, since the word “which” can be a relative pronoun to refer to a non-living thing. </span></span></p><p dir="ltr"><span><span>(A) "</span><span>where"</span><span> and (B) "</span><span>when"</span><span> are incorrect because when they are used as relative adverbs, they equal a preposition and the relative pronoun “which”. if (A) "</span><span>where"</span><span> were the answer, the preposition “in” in the question should be omitted. The sentence would be "Employees ..... of the country where they will reside.".</span></span></p><p dir="ltr"><span><span>(C) "</span><span>what"</span><span> is incorrect because when it is used as a compound relative pronoun, it equals “anything that,” with “anything” serving as the antecedent of an adjective clause and “that” as a relative pronoun in the adjective clause. In other words, “what” can’t be used as a relative pronoun alone. </span></span></p>