Ответ:

Правило: a/an употребляется при первом упоминании предмета, the — при повторном упоминании или когда предмет уже определён контекстом; нулевой артикль возможен с некоторыми устойчивыми сочетаниями.

  1. Last year I spent the summer in a small village. Not far from the village there was a river. The river was shallow and very fast.
  2. The day was coming to an end. It was an unforgettable day.
  3. There lived an old man with his old woman by the very blue sea. They lived in a tumble-down hut for exactly thirty-three years. The old man caught fish with a net, and the old woman spun her yarn.

Артикли: a small village; the village; a river; The river; The day; an unforgettable day; an old man; the very blue sea; a tumble-down hut; The old man; the old woman.