'In' in the first sentence is a preposition as it is followed by the noun to form the prepositional phrase which will function as the adjective to modify the noun 'engineers.'
'Around' in the second sentence is functioning as an adverb because it modifies the verb 'ran' and provides information about where the action took place.
'At Night' in the third sentence is a prepositional phrase as it consists of a preposition plus its object(night) and function as the adverb in the sentence.
'Disgruntled' in the fourth sentence functions as an adjective as it qualifies the noun 'engineers' in the sentence.
'Along the river bank' is also functioning as a prepositional phrase which is acting as an adverb to modify the verb 'strolled.'
'Nightly' is the adverb in the next sentence as it describes the manner in which the action was done.
'Engineers' in the next sentence is the noun as it refers to the class of a people and acts as the subject in the sentence.
'In the union' is also a prepositional phrase which is acting as an adjective to qualify the noun in the sentence.
'Union' in the last sentence is the object of the preposition as it is followed by a preposition and forms the prepositional phrase to act like an adjective in the sentence.
