Final answer:
The correct completion of the sentence is 'du'.
Step-by-step explanation:
The correct completion of the sentence would be du. The sentence is asking 'Do you need a pen?' and in French, the word for 'a pen' is 'un stylo'. However, because 'stylo' is a masculine noun, we need to use the contraction 'du', which means 'of the' in English.
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