TOEIC Reading 5 Exercisee 162

<p><span>The correct answer is (C) on which.&nbsp;</span></p><p><span>In this sentence, we need a relative pronoun to introduce a relative clause that modifies the noun "project". The relative pronoun should refer to "project". "Project' is a thing, so the&nbsp;</span><span>relative clause</span><span>&nbsp;"which" is used. So, the sentence becomes:</span></p><p><strong>"This urgent project which he spent hours working needs additional help to finish on time".</strong></p><p>However, since there's a preposition involved in the relationship between "spend hours working" and "project", you'd need to include the preposition "on" to maintain grammatical correctness.&nbsp;The presence of "on" in the phrase "he spent hours working on" is essential for the structure to make sense.</p><p>So, when we use "on which", the sentence reads:&nbsp;</p><p><strong>"This urgent project on which he spent hours working needs additional help to finish on time."&nbsp;</strong></p><p>Here, "which" refers back to "this urgent project", telling us what he spent hours working on. The preposition "on" is essential because it gives the correct relationship between "spend hours working" and "project".<br></p>