Final answer:
The phrase in bold within the provided sentence is 'of water', which is a prepositional phrase offering more details about the glass.
Step-by-step explanation:
The phrase in bold within the sentence 'Mrs Dlamini gave me a glass full of water.' is 'of water'. This is a prepositional phrase that begins with the preposition 'of' and includes its object 'water', providing additional information about the glass. The full phrase 'a glass full of water' acts as the direct object in the sentence, answering the question 'what' after the verb 'gave'. Therefore, the phrase in bold 'of water' is part of the direct object that completes the idea of what was given.