<p>Let's analyze the sentence:<br></p><p><strong>The attachment (that was sent to the manager yesterday) contained information (___ to the marketing analysis report by the marketing department).</strong></p><p dir="ltr">The part wrapped with "()" is an adjective clause.</p><p dir="ltr">Let's look at the adjective clause: “____ added to the marketing analysis report by the marketing department”<br></p><p dir="ltr">What's missing in the adjective clause is the relative pronoun "which" or "that" and the verb "are added'. The sentence should be:<br></p><p dir="ltr"><strong>The attachment (that was sent to the manager yesterday) contained information (that was added to the marketing analysis report by the marketing department).</strong><br></p><p dir="ltr">In this adjective clause, the relative pronoun “that” is used as a subject of this clause. It can be omitted, but the verb after it must turn into a past participle, “added.” So, the sentence becomes:<br></p><p dir="ltr"><strong>The attachment (that was sent to the manager yesterday) contained information (added to the marketing analysis report by the marketing department).</strong><br></p><p dir="ltr">Thus, the correct answer is (C) added. <br></p>