Concept:Understanding the grammatical structure of a sentence, specifically identifying the roles of different word types like subject, verb, pronoun, and participles.Explanation:Let's break down the sentence "I saw him crossing the bridge."1. Subject: The one performing the action is 'I'.2. Verb: The action is 'saw'.3. Object: The person being seen is 'him'. 'Him' is a pronoun.4. Complement: 'crossing the bridge' describes what 'him' was doing. 'Crossing' is a present participle (verb ending in -ing used to describe an ongoing action).Therefore, the structure of the underlined part (which refers to 'him crossing the bridge' in relation to the subject 'I' and verb 'saw') can be analyzed as Subject ('I') + Verb ('saw') + Pronoun ('him') + Present Participle ('crossing').Answer:Subject + Verb + Pronoun + Present Participle.