Ответ:

  1. T-shirt — the odd one out because boots and shoes are footwear.
  2. boring — the odd one out because cool and fantastic are positive adjectives.
  3. backpack — the odd one out because top and dress are clothes.
  4. cap — the odd one out because trousers and jeans are clothes for the legs.
  5. top — the odd one out because long and big are adjectives.
  6. coat — the odd one out because jacket and skirt are not usually outerwear.