What are they made of and used for?

1.A staw
應該是straw 飲管
A straw is made of plastic. It is used for sucking liquids.

2.A glasses
應該是a pair of glasses 眼鏡
Glasses is made of glass and plastic, sometimes also metal. It is used for letting people with eyesight problems to see clearly.

3.A mittens
應該是a pair of mittens 手套
Mittens is made of wool. It is used for keeping our hands warm.

1. 如果是吸管便是 straw ， 少了r。 而 straw 亦可以是稻草。
A straw is made of plastic and is used for sucking up a drink.
2. glass 是單數。復數 glasses 不能用 a。 意作眼鏡該是 a pair of glasses (一雙的嘛)
咁你可以講：A pair of glasses can be made of plastic, glasses and metal (螺絲); and they are used for correcting vision (視力).
3. 同樣 mittens (手套) 亦是一雙的，一樣要說成 a pair of mittens。呢，只有拇指，拇指外四祇指連在一起的手套呢。
A pair of mittens are made of wool and they are used for keeping the hands warm.