Final answer:
The sentence with the oxymoron is 'Dustin picked up the loosely sealed envelope, unsure of its contents.'
Step-by-step explanation:
The sentence that contains an oxymoron is: Dustin picked up the loosely sealed envelope, unsure of its contents. An oxymoron is a figure of speech that combines contradictory terms, such as 'loosely sealed'. In this sentence, 'loosely' suggests that the envelope is not securely closed, while 'sealed' implies that it is closed tightly. Therefore, this sentence contains an oxymoron.
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