1. They didn't expect us to come back so early. (infinitive construction) 2. It seemed like she didn't hear the noise from the dining room. (impersonal construction) 3. He nodded his head for me to come into the room. (prepositional construction) 4. The teacher insisted that both students apologize. (subjunctive construction) 5. We were looking forward to them visiting us in the summer. (gerund construction) An infinitive construction consists of the word "to" followed by a verb in its infinitive form (base form). It is used to express purpose or intention. In the first sentence, "to come back" is the infinitive construction, indicating the purpose of their actions. An impersonal construction is a grammatical structure in which the subject is not specified, and it is commonly used to describe the weather or the emotions of a group of people. In the second sentence, "It seemed like" is the impersonal construction, expressing the opinion of the speaker. A prepositional construction consists of a preposition followed by a noun phrase. It is used to indicate time, place or manner. In the third sentence, "for me to come into the room" is the prepositional construction, indicating the manner in which he nodded his head. A subjunctive construction is used to express hypothetical or contrary-to-fact situations, wishes and suggestions. In the fourth sentence, "that both students apologize" is the subjunctive construction, indicating the teacher's suggestion or wish. A gerund construction consists of a verb in its -ing form and functions as a noun. It is used to indicate an action as part of a larger sentence. In the fifth sentence, "visiting" is the gerund construction, functioning as the object of the verb "were looking forward to".