Answer:
las clases difíciles
Explanation:
Add an <em>-s</em> to <em>clase</em>, and add an <em>-es</em> to <em>difícil</em> because adjectives have to match the plurality of the word they describe.
Las clases difíciles.
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More than half of the surface of Colombia is unpopulated.
abrazo
Answer: El veloz zorro marrón saltó sobre el perro perezoso.
