Solution:
- shoes (a shirt) - Because shoes are worn on the feet, while a shirt is worn on the top of the body.
- a skirt (a shirt) - Because a skirt is worn on the lower body, while a shirt is worn on the upper body.
- a jacket (trousers) - Because a jacket is worn on the upper body, while trousers are worn on the lower body.
- an umbrella (a skirt) - Because an umbrella is an accessory used for protection from rain or sun, while a skirt is an item of clothing.
Answer: 1-b, 2-c, 3-a, 4-d.