The biodegradable articles are
(a) paper
(b) woollen clothes
(c) wood
(f) peels of vegetables

Plastic is non-reactive material. When left exposed to moisture and air, it does not react with air and water which are essential for corrosion, therefore does not rust

Thermoplastics get deformed easily on heating and can be bent easily on heating. On the other hand, thermosetting plastics when moulded once cannot be softened on heating.
Thermoplastics ➡️ Polythene and PVC
Thermosetting plastics➡️Bakelite and melamine.

No, handle and bristles of a toothbrush should not be made of the same material because the handle should be hard while bristles should be made of the soft materials. Bristles should be soft so that it does not harm the gum of teeth. Handle should be made of hard material so that it gives the firm grip.

(a) The handles of saucepan are made up of thermosetting plastics because it is a poor (bad) conductor of heat and thus, we can hold the hot saucepan safely without getting our hands burnt.
(b) Electric plugs/switches/plug boards are made up of thermosetting plastics because it is a bad conductor of electricity and thus, protects us from electric current passing through them

Natural polymer occuring in plants are cellulose, starch, etc

It is used for non-stick coating in cookwares.

Polyester is the polymer made up of the repeating units of ester. Terylene is the commonly used polyester.

Polyester

(a) Nikita was aware that plastic is a non-biodegradable material. Disposal of plastic is a major problem. It is not easily decomposed by natural process. So, to avoid the use of plastic she prefer to take steel lunch box.
(b) No, plastic materials are not environment friendly since, it takes several years to decompose and causes environmental pollution. Besides, in the burning process it releases lots of poisonous fumes (gases) into the atmosphere causing air pollution.
(c) Nikita is very aware, sensible and intelligent girl.