Which diagnosis explains why this sentence is nonstandard? That is the gallery where the students visited yesterday.
Gallery cannot be an antecedent of any relative clause.
Where is reserved for outdoor places.
Visited needs the gallery as its direct object, so a relative pronoun is needed.✓Ճիշտ պատասխան
Yesterday cannot occur inside a relative clause.
Բացատրություն
Visited is transitive here, and the gallery is what the students visited, so the gap is an object gap. Where supplies a location relation instead and therefore cannot perform the grammatical job the verb requires.