carbohydrates, polysaccharides

1) Polysaccharide is a kind of carbohydrate?

It is correct. (see Q no. 2)

2) Carbohydrates can be classified into 4 groups: mono, di, oligo and poly?

Carbohydrates are usually classified into 3 groups: mono, di and poly
For oligosaccharide, as it can contain 2 to 10 sugar, some of them are disaccharide also and also, for carbohydrates with 3 or more sugar it can be called poly already.

3) starch, glucose are examples of polysaccharides?

Oh this is wrong . Starch is an example of polysaccharide as it contains a large number of glucose inside (usually about 10 to 500)
However, glucose is an example of monosaccharide as its structure contains one simple sugar only. Many glucose make up starch.

4) only polysaccharides are natural polymers? How about mono and di?

This is wrong also. Almost every carbohydrates are natural polymers . For instance, starch (poly) exists in lots of crops plants (e.g. rice), sucrose (di) is present in most plants, which it is useful to act as a transportational carbohydrate, glucose is converted into sucrose before it is relocated to elsewhere in plants. While glucose, fructose and galactose are mono that exists almost everwhere in nature, for example in fruits, flowers, animals, or even underground from the dead plant tissues.

Hope these can help you la!!! =]
If you do not understand you can further ask me!!! =]
Cheers!

1 > 當然 , 多「西唐」是由碳水化合物的一種

2 > 應該話saccharide可以分做 4種 : 單 , 雙 , 寡 , 多

3 > 錯 , starch 係 glucose 一種 , 係poly , glucose 係 單「西唐」

starch is stored in roots, tubers, leaves, rhizomes and bulbs in plants.

4 > 好似肝糖同cellulus一樣都係以glucose做單元 , 只係連接方式唔同先會表現到 所以polysacchardes 好自然係polymer . 如果係mono的話就會叫做monomer