Final answer:
The correct pair of adjectives that completes the sentence is 'traditionnels, de soie'.
Step-by-step explanation:
The correct pair of adjectives that completes the sentence 'Ils veulent acheter des pantalons' is 'traditionnels, de soie'.
The adjective 'traditionnels' (traditional) describes the style or type of the pants, and 'de soie' (made of silk) describes the material from which the pants are made.
For example, the sentence 'Ils veulent acheter des pantalons traditionnels de soie' translates to 'They want to buy traditional silk pants'.
Learn more about French adjectives