Laquelle de ces phrases est correcte ?

The correct sentence is Il n'aime pas la salade, meaning "He does not like salad." This sentence follows the standard French word order and negation pattern correctly.

In French, a basic negative sentence follows the structure: Subject + ne + verb + pas + complement. Breaking down the correct sentence:

• Il (subject: he)
• n' (ne, elided before the vowel of aime)
• aime (verb: likes/loves)
• pas (second part of negation)
• la salade (complement: the salad)

The other options contain errors:

• Elle s'est lave les mains has an agreement error. With reflexive verbs in the passé composé followed by a direct object, the past participle should not agree with the subject. The correct form would be "Elle s'est lavé les mains" (with an accent on the "e" of lavé).
• Elle salade n'aime pas has completely jumbled word order. The subject, object, verb, and negation are not in any valid French order.
• Il la salade n'aime pas also has incorrect word order. The object "la salade" cannot appear between the subject and the negated verb.